Let me be clear: This revolver is the first step towards the Second Model. It was submitted to the Russians because Ordintetz wanted changes to make the recoil more manageable. It is mechanically a First Model with none of the mechanical changes that are seen in the second model.
The second step in the evolution was the revolver which is now in the Connecticut state library with the knuckle on the frame.

BTW it definitely predates the Merwin Hulbert by about 4 years so they didn't copy that grip shape.
Joe