Bulova 1962 Military Issue

I recently purchased a Vietnam issue Mil-W-3818A with an A17A case back. I'm sure it was common to have mismatched parts but I am looking for a correct case back. That is not my reason for posting. When I opened the back it has a Bulova 15 jewel 10BNCH movement which is correct for the 3818A variant. I was surprised to see what appears to be 2 date codes. It has the usual small date code of M2 (1962) but next to BULOVA WATCH Co, I see a stamped M8 which is 1968. Is this also a date code? Bulova stopped making watches for the military in 1962. 

Sorry If the pictures aren't great, I tried my best.   I appreciate any information you can give. Thank you!