If your deceased husband (sorry for your loss) was actually in the USMC or any of the other military services and was discharged he will have a DD214 document. The DD214 is legal poof of his service. If you cannot locate this document, contact HQ USMC Washington DC. You will need his dates of service, SSN, rank, and MOS. They will direct you to the proper channel to pursue your inquiry. If HQ USMC doesn't have a record of his service then he probably didn't serve.Good Luck