Guys, just acquired an A1 with strange markings least I think so. SN is 54847SF dod 8/53. Hood # 2B1605. Willis manufacturing data plate behind seat is missing. Looks like the unit was brush painted OD. A lot of paint is coming off and the base coat is dark blue. The ID plate has ord dept as procuring agency and maintaining agency. Anyone got an educated guess on service, what SF means, is that a standard hood number for '53 A1? thank you