Welcome to the Forum. The gun is not a Smith & Wesson. Looking at the hammer, there is no hammer mounted firing pin. Looking at the trigger, it looks like a Hopkins & Allen Safety Police model with S&W stocks.

The gun has been heavily buffed and re-plated at some point in its life, so not any dollar value, but family heirlooms normally have incalculable value to the family!!

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Gary
SWCA 2515