Dan Shuey mentions the Hotchkiss 1 pounder cartridges in W.R.A.Co Headstamped Cartridges and Their Variations, Vol 1, page 350. ‘Winchester manufactured a wide variety of artillery casings for the U. S. Government ranging from 1 lb. Hotchkiss Deck and Mountain Guns (37mm) to 8" rifle.’ He goes on to say ‘the small Hotchkiss one-pound cartridges were not (?) more commonly known as 37m/m. Casings for the U.S. Navy and various 3" and 4" sizes were made as well as 4.7" cases in both howitzer and gun sizes for the U.S. Army.’ This 4.7" size is the 120mm that I included the picture of.
Looking in my copy of the 1907 Bannerman catalog, I find a number of different Navy deck guns, but found none of the Army’s mountain guns.
According to the 1878 Report of the Chief of Ordnance, the first Hotchkiss 'Mountain Breech-Loading Rifle was issued to the Department of Dakota in 1877 and tested in the field that summer. The caliber was 1.65", a little larger than our 37mm examples. In 1879, procurements by the Army included 10 Hotchkiss mountain 1.65" guns and 4 Hotchkiss revolving 1.5" guns, as well as 2000 rounds of 1.5" ammunition. These would be pretty close to 37mm, but the diagrams included in the 1879 report show a shorter shell, of the Hotchkiss patent style that are formed of wrapped steel with the head attached with three rivets. I have one of these shells somewhere here and will try to locate it to get a picture posted. I’ll also post a picture of the revolving cannon.