The middle projectile is for the Hotchkiss 37 x 307r loading. a smaller version of the more common 3 pdr. This appears to be the only Hotchkiss 37mm with the 3 ribbed banding as found on their 47mm, 57mm and 75mm types. The base as yet still in place is like the regular Hotchkiss base marked HOTCHKISS PATENT, I expect it uses the standard internal fuse assembly. Norway bought these and reloaded the casings and eventually made their own when they could be no longer supplied. These casing as they were used over and over were shortened to 37x302r size. I would like to locate a Hotchkiss 37x307 case for this - seems hopeless but who knows whats around. The left and right projectiles are for comparison.