Very handy for identifying Vietnam period helmets.   Contract Number Manufacturer Date Proximity USMC Project Number 5501 DC & TSC DIR. MFG. 4 February 1959 USMC Project Number 5850 DC & TSC DIR. MFG. 10 December 1959 P.O. No. 5002-62 1962 DSA 1-811-C-62 1962 DSA 1-1940-63-C 1963 DSA 1-3839-64-C 1964 DSA 1-4540-64-C 1964 DSA 1-6600-65-C Late 1964 – 1965 DSA 1-6680-65-C Late 1964 - 1965 Contract No. 5432 1964* Contract No. 5626 1964* Contract No. 5654