Or a dealer could have made the exchange. Say he had a customer who wanted a certain combination of barrel length and stocks. If the dealer had several N-Frame revolvers on hand, he could have changed things around as required to make the sale.

Or your revolver could have been one of a shipment sent to a police department. During routine cleaning of multiple revolvers, the armorer may not have been any too choosey about which revolver got which stocks.

You could spend $75 on a factory letter to verify what type of stocks originally shipped with your revolver, but that is all it will tell you. The letter can't tell you if it left the factory with a matching serial number on the stocks.

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