I have what appears to be an 57mm 6 pdr, case headstamped U.M.C. Co. BRIDGEPORT CONN. U.S.A. This case is most likely before 1911 as that is when U.M.C. and Remington merged. The case is 57mm cal (Bottle-Necked) with a length of 307mm. The head is 75mm. Is this a Hotchkiss or a Vickers case type? What is the difference between them?