diff --git a/polygon/modelclass.py b/polygon/modelclass.py
new file mode 100644
index 00000000..179e2689
--- /dev/null
+++ b/polygon/modelclass.py
@@ -0,0 +1,23 @@
+import inspect
+from dataclasses import dataclass
+
+
+def modelclass(cls):
+    cls = dataclass(cls)
+    attributes = [
+        a
+        for a in cls.__dict__["__annotations__"].keys()
+        if not a.startswith("__") and not inspect.isroutine(a)
+    ]
+
+    def init(self, *args, **kwargs):
+        for (i, a) in enumerate(args):
+            if i < len(attributes):
+                self.__dict__[attributes[i]] = a
+        for (k, v) in kwargs.items():
+            if k in attributes:
+                self.__dict__[k] = v
+
+    cls.__init__ = init
+
+    return cls
diff --git a/polygon/rest/models/aggs.py b/polygon/rest/models/aggs.py
index b14d4969..72aa0db2 100644
--- a/polygon/rest/models/aggs.py
+++ b/polygon/rest/models/aggs.py
@@ -1,8 +1,8 @@
-from dataclasses import dataclass
 from typing import Optional
+from ...modelclass import modelclass
 
 
-@dataclass
+@modelclass
 class Agg:
     "Contains aggregate data for a given ticker symbol over a given date range in a custom time window size."
     open: Optional[float] = None
@@ -28,7 +28,7 @@ def from_dict(d):
         )
 
 
-@dataclass
+@modelclass
 class GroupedDailyAgg:
     "Contains daily open, high, low, and close (OHLC) data for a given date."
     ticker: Optional[str] = None
@@ -56,7 +56,7 @@ def from_dict(d):
         )
 
 
-@dataclass
+@modelclass
 class DailyOpenCloseAgg:
     "Contains data for open, close and afterhours prices of a ticker symbol on a specified date."
     after_hours: Optional[float] = None
@@ -86,7 +86,7 @@ def from_dict(d):
         )
 
 
-@dataclass
+@modelclass
 class PreviousCloseAgg:
     "Contains data for the previous day's open, high, low, and close (OHLC) of the specified stock ticker."
     ticker: Optional[str] = None
diff --git a/polygon/rest/models/conditions.py b/polygon/rest/models/conditions.py
index e94984a8..3fc0d776 100644
--- a/polygon/rest/models/conditions.py
+++ b/polygon/rest/models/conditions.py
@@ -1,8 +1,8 @@
 from typing import Optional, List
-from dataclasses import dataclass
+from ...modelclass import modelclass
 
 
-@dataclass
+@modelclass
 class SipMapping:
     "Contains data for a mapping to a symbol for each SIP that has a given condition."
     CTA: Optional[str] = None
@@ -14,7 +14,7 @@ def from_dict(d):
         return SipMapping(**d)
 
 
-@dataclass
+@modelclass
 class Consolidated:
     "Contains data for aggregation rules on a consolidated (all exchanges) basis."
     updates_high_low: Optional[bool] = None
@@ -26,7 +26,7 @@ def from_dict(d):
         return Consolidated(**d)
 
 
-@dataclass
+@modelclass
 class MarketCenter:
     "Contains data for aggregation rules on a per-market-center basis."
     updates_high_low: Optional[bool] = None
@@ -38,7 +38,7 @@ def from_dict(d):
         return MarketCenter(**d)
 
 
-@dataclass
+@modelclass
 class UpdateRules:
     "Contains data for a list of aggregation rules."
     consolidated: Optional[Consolidated] = None
@@ -56,7 +56,7 @@ def from_dict(d):
         )
 
 
-@dataclass
+@modelclass
 class Condition:
     "Condition contains data for a condition that Polygon.io uses."
     abbreviation: Optional[str] = None
diff --git a/polygon/rest/models/dividends.py b/polygon/rest/models/dividends.py
index 2ae3ba80..1abe5dc5 100644
--- a/polygon/rest/models/dividends.py
+++ b/polygon/rest/models/dividends.py
@@ -1,8 +1,8 @@
 from typing import Optional
-from dataclasses import dataclass
+from ...modelclass import modelclass
 
 
-@dataclass
+@modelclass
 class Dividend:
     "Dividend contains data for a historical cash dividend, including the ticker symbol, declaration date, ex-dividend date, record date, pay date, frequency, and amount."
     cash_amount: Optional[float] = None
diff --git a/polygon/rest/models/exchanges.py b/polygon/rest/models/exchanges.py
index ef0254fe..cd93a7d9 100644
--- a/polygon/rest/models/exchanges.py
+++ b/polygon/rest/models/exchanges.py
@@ -1,8 +1,8 @@
 from typing import Optional
-from dataclasses import dataclass
+from ...modelclass import modelclass
 
 
-@dataclass
+@modelclass
 class Exchange:
     "Exchange contains data for a condition that Polygon.io uses."
     acronym: Optional[str] = None
diff --git a/polygon/rest/models/financials.py b/polygon/rest/models/financials.py
index 6f578187..85a63e37 100644
--- a/polygon/rest/models/financials.py
+++ b/polygon/rest/models/financials.py
@@ -1,8 +1,8 @@
 from typing import Optional, Dict
-from dataclasses import dataclass
+from ...modelclass import modelclass
 
 
-@dataclass
+@modelclass
 class DataPoint:
     "An individual financial data point."
     formula: Optional[str] = None
@@ -17,7 +17,7 @@ def from_dict(d):
         return DataPoint(**d)
 
 
-@dataclass
+@modelclass
 class ExchangeGainsLosses:
     "Contains exchange gains losses data for a cash flow statement."
     formula: Optional[str] = None
@@ -32,7 +32,7 @@ def from_dict(d):
         return ExchangeGainsLosses(**d)
 
 
-@dataclass
+@modelclass
 class NetCashFlow:
     "Contains net cash flow data for a cash flow statement."
     formula: Optional[str] = None
@@ -47,7 +47,7 @@ def from_dict(d):
         return NetCashFlow(**d)
 
 
-@dataclass
+@modelclass
 class NetCashFlowFromFinancingActivities:
     "Contains net cash flow from financing activities data for a cash flow statement."
     formula: Optional[str] = None
@@ -62,7 +62,7 @@ def from_dict(d):
         return NetCashFlowFromFinancingActivities(**d)
 
 
-@dataclass
+@modelclass
 class CashFlowStatement:
     "Contains cash flow statement data."
     exchange_gains_losses: Optional[ExchangeGainsLosses] = None
@@ -88,7 +88,7 @@ def from_dict(d):
         )
 
 
-@dataclass
+@modelclass
 class ComprehensiveIncomeLoss:
     "Contains comprehensive income loss data for comprehensive income."
     formula: Optional[str] = None
@@ -103,7 +103,7 @@ def from_dict(d):
         return ComprehensiveIncomeLoss(**d)
 
 
-@dataclass
+@modelclass
 class ComprehensiveIncomeLossAttributableToParent:
     "Contains comprehensive income loss attributable to parent data for comprehensive income."
     formula: Optional[str] = None
@@ -118,7 +118,7 @@ def from_dict(d):
         return ComprehensiveIncomeLossAttributableToParent(**d)
 
 
-@dataclass
+@modelclass
 class OtherComprehensiveIncomeLoss:
     "Contains other comprehensive income loss data for comprehensive income."
     formula: Optional[str] = None
@@ -133,7 +133,7 @@ def from_dict(d):
         return OtherComprehensiveIncomeLoss(**d)
 
 
-@dataclass
+@modelclass
 class ComprehensiveIncome:
     "Contains comprehensive income data."
     comprehensive_income_loss: Optional[ComprehensiveIncomeLoss] = None
@@ -161,7 +161,7 @@ def from_dict(d):
         )
 
 
-@dataclass
+@modelclass
 class BasicEarningsPerShare:
     "Contains basic earning per share data for an income statement."
     formula: Optional[str] = None
@@ -176,7 +176,7 @@ def from_dict(d):
         return BasicEarningsPerShare(**d)
 
 
-@dataclass
+@modelclass
 class CostOfRevenue:
     "Contains cost of revenue data for an income statement."
     formula: Optional[str] = None
@@ -191,7 +191,7 @@ def from_dict(d):
         return CostOfRevenue(**d)
 
 
-@dataclass
+@modelclass
 class GrossProfit:
     "Contains gross profit data for an income statement."
     formula: Optional[str] = None
@@ -206,7 +206,7 @@ def from_dict(d):
         return GrossProfit(**d)
 
 
-@dataclass
+@modelclass
 class OperatingExpenses:
     "Contains operating expenses data for an income statement."
     formula: Optional[str] = None
@@ -221,7 +221,7 @@ def from_dict(d):
         return OperatingExpenses(**d)
 
 
-@dataclass
+@modelclass
 class Revenues:
     "Contains revenues data for an income statement."
     formula: Optional[str] = None
@@ -236,7 +236,7 @@ def from_dict(d):
         return Revenues(**d)
 
 
-@dataclass
+@modelclass
 class IncomeStatement:
     "Contains income statement data."
     basic_earnings_per_share: Optional[BasicEarningsPerShare] = None
@@ -264,7 +264,7 @@ def from_dict(d):
         )
 
 
-@dataclass
+@modelclass
 class Financials:
     "Contains financial data."
     balance_sheet: Optional[Dict[str, DataPoint]] = None
@@ -290,7 +290,7 @@ def from_dict(d):
         )
 
 
-@dataclass
+@modelclass
 class StockFinancial:
     "StockFinancial contains historical financial data for a stock ticker."
     cik: Optional[str] = None
diff --git a/polygon/rest/models/markets.py b/polygon/rest/models/markets.py
index 3a3bbbc2..0ef769be 100644
--- a/polygon/rest/models/markets.py
+++ b/polygon/rest/models/markets.py
@@ -1,8 +1,8 @@
 from typing import Optional
-from dataclasses import dataclass
+from ...modelclass import modelclass
 
 
-@dataclass
+@modelclass
 class MarketCurrencies:
     "Contains currency market status data."
     crypto: Optional[str] = None
@@ -13,7 +13,7 @@ def from_dict(d):
         return MarketCurrencies(**d)
 
 
-@dataclass
+@modelclass
 class MarketExchanges:
     "Contains exchange market status data."
     nasdaq: Optional[str] = None
@@ -25,7 +25,7 @@ def from_dict(d):
         return MarketExchanges(**d)
 
 
-@dataclass
+@modelclass
 class MarketHoliday:
     "MarketHoliday contains data for upcoming market holidays and their open/close times."
     close: Optional[str] = None
@@ -40,7 +40,7 @@ def from_dict(d):
         return MarketHoliday(**d)
 
 
-@dataclass
+@modelclass
 class MarketStatus:
     "MarketStatus contains data for the current trading status of the exchanges and overall financial markets."
     after_hours: Optional[bool] = None
diff --git a/polygon/rest/models/quotes.py b/polygon/rest/models/quotes.py
index c19e711a..c4f2c00f 100644
--- a/polygon/rest/models/quotes.py
+++ b/polygon/rest/models/quotes.py
@@ -1,8 +1,8 @@
 from typing import Optional, List
-from dataclasses import dataclass
+from ...modelclass import modelclass
 
 
-@dataclass
+@modelclass
 class Quote:
     "Quote contains quote data for a specified ticker symbol."
     ask_exchange: Optional[int] = None
@@ -24,7 +24,7 @@ def from_dict(d):
         return Quote(**d)
 
 
-@dataclass
+@modelclass
 class LastQuote:
     "LastQuote contains data for the most recent NBBO (Quote) tick for a given stock."
     ticker: Optional[str] = None
@@ -62,7 +62,7 @@ def from_dict(d):
         )
 
 
-@dataclass
+@modelclass
 class ForexQuote:
     "Contains data for a forex quote."
     ask: Optional[float] = None
@@ -75,7 +75,7 @@ def from_dict(d):
         return ForexQuote(**d)
 
 
-@dataclass
+@modelclass
 class LastForexQuote:
     "ForexLastQuote contains data for the last quote tick for a forex currency pair."
     last: Optional[ForexQuote] = None
@@ -89,7 +89,7 @@ def from_dict(d):
         )
 
 
-@dataclass
+@modelclass
 class RealTimeCurrencyConversion:
     "RealTimeCurrencyConversion contains data for currency conversions using the latest market conversion rates."
     converted: Optional[float] = None
diff --git a/polygon/rest/models/snapshot.py b/polygon/rest/models/snapshot.py
index db2e3366..072b8421 100644
--- a/polygon/rest/models/snapshot.py
+++ b/polygon/rest/models/snapshot.py
@@ -1,11 +1,11 @@
-from dataclasses import dataclass
 from typing import Optional, List, Dict
 from .aggs import Agg
 from .quotes import LastQuote
 from .trades import LastTrade
+from ...modelclass import modelclass
 
 
-@dataclass
+@modelclass
 class MinuteSnapshot:
     "Most recent minute bar."
     accumulated_volume: Optional[float] = None
@@ -29,7 +29,7 @@ def from_dict(d):
         )
 
 
-@dataclass
+@modelclass
 class TickerSnapshot:
     "Contains the most up-to-date market data for all traded ticker symbols."
     day: Optional[Agg] = None
@@ -61,7 +61,7 @@ def from_dict(d):
         )
 
 
-@dataclass
+@modelclass
 class DayOptionContractSnapshot:
     "Contains data for the most recent daily bar in an options contract."
     change: Optional[float] = None
@@ -80,7 +80,7 @@ def from_dict(d):
         return DayOptionContractSnapshot(**d)
 
 
-@dataclass
+@modelclass
 class OptionDetails:
     "Contains details for an options contract."
     contract_type: Optional[str] = None
@@ -95,7 +95,7 @@ def from_dict(d):
         return OptionDetails(**d)
 
 
-@dataclass
+@modelclass
 class LastQuoteOptionContractSnapshot:
     "Contains data for the most recent quote in an options contract."
     ask: Optional[float] = None
@@ -111,7 +111,7 @@ def from_dict(d):
         return LastQuoteOptionContractSnapshot(**d)
 
 
-@dataclass
+@modelclass
 class Greeks:
     "Contains data for the greeks in an options contract."
     delta: Optional[float] = None
@@ -124,7 +124,7 @@ def from_dict(d):
         return Greeks(**d)
 
 
-@dataclass
+@modelclass
 class UnderlyingAsset:
     "Contains data for the underlying stock in an options contract."
     change_to_break_even: Optional[float] = None
@@ -138,7 +138,7 @@ def from_dict(d):
         return UnderlyingAsset(**d)
 
 
-@dataclass
+@modelclass
 class OptionContractSnapshot:
     "Contains data for the snapshot of an option contract of a stock equity."
     break_even_price: Optional[float] = None
@@ -172,7 +172,7 @@ def from_dict(d):
         )
 
 
-@dataclass
+@modelclass
 class OrderBookQuote:
     "Contains data for a book bid or ask."
     price: Optional[float] = None
@@ -186,7 +186,7 @@ def from_dict(d):
         )
 
 
-@dataclass
+@modelclass
 class SnapshotTickerFullBook:
     "Contains the current level 2 book of a single ticker. This is the combined book from all of the exchanges."
     ticker: Optional[str] = None
diff --git a/polygon/rest/models/splits.py b/polygon/rest/models/splits.py
index 037a3e1e..93244c50 100644
--- a/polygon/rest/models/splits.py
+++ b/polygon/rest/models/splits.py
@@ -1,8 +1,8 @@
 from typing import Optional
-from dataclasses import dataclass
+from ...modelclass import modelclass
 
 
-@dataclass
+@modelclass
 class Split:
     "Split contains data for a historical stock split, including the ticker symbol, the execution date, and the factors of the split ratio."
     execution_date: Optional[str] = None
diff --git a/polygon/rest/models/tickers.py b/polygon/rest/models/tickers.py
index 4f650baa..0b5e11f0 100644
--- a/polygon/rest/models/tickers.py
+++ b/polygon/rest/models/tickers.py
@@ -1,8 +1,8 @@
 from typing import Optional, List
-from dataclasses import dataclass
+from ...modelclass import modelclass
 
 
-@dataclass
+@modelclass
 class CompanyAddress:
     "Contains address data for a ticker detail."
     address1: Optional[str] = None
@@ -17,7 +17,7 @@ def from_dict(d):
         return CompanyAddress(**d)
 
 
-@dataclass
+@modelclass
 class Branding:
     "Contains branding data for a ticker detail."
     icon_url: Optional[str] = None
@@ -31,7 +31,7 @@ def from_dict(d):
         return Branding(**d)
 
 
-@dataclass
+@modelclass
 class Publisher:
     "Contains publisher data for ticker news."
     favicon_url: Optional[str] = None
@@ -44,7 +44,7 @@ def from_dict(d):
         return Publisher(**d)
 
 
-@dataclass
+@modelclass
 class Ticker:
     "Ticker contains data for a specified ticker symbol."
     active: Optional[bool] = None
@@ -69,7 +69,7 @@ def from_dict(d):
         return Ticker(**d)
 
 
-@dataclass
+@modelclass
 class TickerDetails:
     "TickerDetails contains data for a specified ticker symbol."
     active: Optional[bool] = None
@@ -133,7 +133,7 @@ def from_dict(d):
         )
 
 
-@dataclass
+@modelclass
 class TickerNews:
     "TickerDetails contains data for news articles relating to a stock ticker symbol."
     amp_url: Optional[str] = None
@@ -167,7 +167,7 @@ def from_dict(d):
         )
 
 
-@dataclass
+@modelclass
 class TickerTypes:
     "TickerTypes contains data for ticker types."
     asset_class: Optional[str] = None
diff --git a/polygon/rest/models/trades.py b/polygon/rest/models/trades.py
index 09825097..25b9adc7 100644
--- a/polygon/rest/models/trades.py
+++ b/polygon/rest/models/trades.py
@@ -1,8 +1,8 @@
 from typing import Optional, List
-from dataclasses import dataclass
+from ...modelclass import modelclass
 
 
-@dataclass
+@modelclass
 class Trade:
     "Trade contains trade data for a specified ticker symbol."
     conditions: Optional[List[int]] = None
@@ -23,7 +23,7 @@ def from_dict(d):
         return Trade(**d)
 
 
-@dataclass
+@modelclass
 class LastTrade:
     "Contains data for the most recent trade for a given ticker symbol."
     ticker: Optional[str] = None
@@ -59,7 +59,7 @@ def from_dict(d):
         )
 
 
-@dataclass
+@modelclass
 class CryptoTrade:
     "Contains data for a crypto trade."
     conditions: Optional[List[int]] = None
diff --git a/polygon/websocket/models/models.py b/polygon/websocket/models/models.py
index 53f7743d..75232007 100644
--- a/polygon/websocket/models/models.py
+++ b/polygon/websocket/models/models.py
@@ -1,9 +1,9 @@
 from typing import Optional, List, Union, NewType
 from .common import EventType
-from dataclasses import dataclass
+from ...modelclass import modelclass
 
 
-@dataclass
+@modelclass
 class EquityAgg:
     "EquityAgg contains aggregate data for either stock tickers or option contracts."
     event_type: Optional[Union[str, EventType]] = None
@@ -41,7 +41,7 @@ def from_dict(d):
         )
 
 
-@dataclass
+@modelclass
 class CurrencyAgg:
     "CurrencyAgg contains aggregate data for either forex currency pairs or crypto pairs."
     event_type: Optional[Union[str, EventType]] = None
@@ -73,7 +73,7 @@ def from_dict(d):
         )
 
 
-@dataclass
+@modelclass
 class EquityTrade:
     "EquityTrade contains trade data for either stock tickers or option contracts."
     event_type: Optional[Union[str, EventType]] = None
@@ -103,7 +103,7 @@ def from_dict(d):
         )
 
 
-@dataclass
+@modelclass
 class CryptoTrade:
     "CryptoTrade contains trade data for a crypto pair."
     event_type: Optional[Union[str, EventType]] = None
@@ -131,7 +131,7 @@ def from_dict(d):
         )
 
 
-@dataclass
+@modelclass
 class EquityQuote:
     "EquityQuote contains quote data for either stock tickers or option contracts."
     event_type: Optional[Union[str, EventType]] = None
@@ -165,7 +165,7 @@ def from_dict(d):
         )
 
 
-@dataclass
+@modelclass
 class ForexQuote:
     "ForexQuote contains quote data for a forex currency pair."
     event_type: Optional[Union[str, EventType]] = None
@@ -187,7 +187,7 @@ def from_dict(d):
         )
 
 
-@dataclass
+@modelclass
 class CryptoQuote:
     "CryptoQuote contains quote data for a crypto pair."
     event_type: Optional[Union[str, EventType]] = None
@@ -215,7 +215,7 @@ def from_dict(d):
         )
 
 
-@dataclass
+@modelclass
 class Imbalance:
     "Imbalance contains imbalance event data for a given stock ticker symbol."
     event_type: Optional[Union[str, EventType]] = None
@@ -245,7 +245,7 @@ def from_dict(d):
         )
 
 
-@dataclass
+@modelclass
 class LimitUpLimitDown:
     "LimitUpLimitDown contains LULD event data for a given stock ticker symbol."
     event_type: Optional[Union[str, EventType]] = None
@@ -271,7 +271,7 @@ def from_dict(d):
         )
 
 
-@dataclass
+@modelclass
 class Level2Book:
     "Level2Book contains level 2 book data for a given crypto pair."
     event_type: Optional[Union[str, EventType]] = None
diff --git a/test_rest/test_modelclass.py b/test_rest/test_modelclass.py
new file mode 100644
index 00000000..651a6393
--- /dev/null
+++ b/test_rest/test_modelclass.py
@@ -0,0 +1,51 @@
+from polygon.rest.models import Agg
+from base import BaseTest
+
+
+class ModelclassTest(BaseTest):
+    def test_extra_field(self):
+        a = Agg(
+            open=1.5032,
+            high=1.5064,
+            low=1.4489,
+            close=1.4604,
+            volume=642646396.0,
+            vwap=1.469,
+            timestamp=1112331600000,
+            transactions=82132,
+        )
+        b = Agg(
+            open=1.5032,
+            high=1.5064,
+            low=1.4489,
+            close=1.4604,
+            volume=642646396.0,
+            vwap=1.469,
+            timestamp=1112331600000,
+            transactions=82132,
+            extra_field=22,
+        )
+        self.assertEqual(a, b)
+
+    def test_init_order(self):
+        a = Agg(
+            open=1.5032,
+            high=1.5064,
+            low=1.4489,
+            close=1.4604,
+            volume=642646396.0,
+            vwap=1.469,
+            timestamp=1112331600000,
+            transactions=82132,
+        )
+        b = Agg(
+            1.5032,
+            1.5064,
+            1.4489,
+            1.4604,
+            642646396.0,
+            1.469,
+            1112331600000,
+            82132,
+        )
+        self.assertEqual(a, b)