Tony, The PE & M Co. marking is Poole Engineering and Machine Company of Baltimore,Maryland USA. They also subcontracted parts for the 37mm Infantry cannon to the Maryland Pressed Steel Company in Hagerstown, Maryland. The cannon was proof fired near the Hagerstown Factory in ClearSpring , Maryland. It is interesting that the barracks to house personnel and a long concrete trench with three bunkers in a forgotten farm field abandon since 1919 still exist to this day. Only 300 US built 37mm Infantry guns made it to Europe before the war ended. Kind Regards Bob