The 37mm M16 case for the rounds used in the WWII and later weapons such as the M3A1 AT Gun and the M5A1 and M6 Tank guns is a fairly common case. The projectile in the loaded round in the photo is a 1941 dated M63 HE. The two empty cases are experimentals that are unheadstamped so I have no idea of the date of the experimentation. The recoilless case is a lacquered steel variation. It has apparently been fired because there are crimps on the neck and the inside of the case is blackened. There is no primer present. The other case has a brass base and a black plastic body. It is 8 13/16 inches long instead of the standard 8 1/2 inches, the difference being in the length of the neck. I do not have any official information on either case.