On display in the Springfield Armory Display of S&W guns was an Army Model tip-up Smith, a one-of-a-kind revolver.
This gun was a large frame tip-up, in .41 caliber rimfire, I believe. It was like the early .22 and .32 rimfires, except for size. Supposedly this was made for Army consideration around 1865 or 1866, and just preceeded the top-break No. 3 revolver purchased by the Army.
I have not seen the document, but have seen quotations to the effect that it was rejected because it should be " of .44 caliber and central fire." This led to the submittal and purchase of the No. 3 .44 S&W top break model by the Army in 1866 or so.