Jerry, I see pistol grips on American breechloaders from the latest part of the 1870s on. Wesson, Baker, L C Smith, Clark and Sneider and others show this design. I think in the 1880s, and on, most American makers used a pistol grip. Smith , Ithaca, Baker, Lefever, etc come to mind. I am not sure you can call this a "standard", as in the US, Britain, and the continent you can find many examples of each style.

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