I have a Thomas & Thomas handbook and have looked through it thoroughly. The only bullet that comes close to this one is the .40 LeMat (T&T #22), a French manufactured revolver for the Confederate troops. If it is a .40 LeMat I have another predicament. I found it at the Indian Wars site I hunt that was used from 1865-1870. Considering the LeMat was only used by the Confederates, how do you suppose it ended up at a western fort site? Souvenir from the war? Captured revolver that was being used by US Army personnel? Former Confederate troop who transferred to the US Army and was serving in the west? As far as I'm aware there were no Galvanized Yankees at this site. It measures .417" diameter (at the widest point), .645" length and 157 gr for weight. Pretty close to what the T&T handbook lists for the .40 LeMat.