How does an E6 have 6 service stripes?

PFC is definitely on to something. What is RCP for E6 nowadays?

You can retire as an E-6. Nothing wrong with that.

It makes perfect sense, I retired from active duty with 20 years and 12 days service which means for the last 2 years of my active duty I was required to have 6 services stripes reflecting 18 years of service but less than 21

Back in the 1980 and pre-war in general, getting out at E6 was quite routine for some folks. Just do your job, hit the target as best you can, show up and do what's asked of you. Not hard to do back in the day...... Becoming an E7 and a Platoon SGT was not always in the cards for some folks, sometimes they just were not presented with the option or in may cases, a personal decision that they just didn't want to deal with it.

He could be in the National Guard.

Happens quite frequently in the Navy and I assume other branches are the same, depends upon your Rating/MOS. Some jobs it's damn near impossible to advance.

It could be possible that he was in the guard for a spell before going active duty as well.

I was in the US Navy. They use a stripe for every four years. I knew the Army was three years per stripe, but was confused about how each level (E-1, E-2) appeared on the sleeves. I am trying to convince a nephew that serving is a special way to give, and earn respect and experience, and grow up ! Something I was scheduled to do in 1970, but changed my mind. My best friend did go in on 16 Jun 1970, into the Warrant Officer program for helicopter pilots. I later became a pilot for fixed wing, but regret not getting helo training.
Thank you very much !

Con Gubser

Could be that he is an MP. They promote slow as hell.....

A number of reasons could have been a screw up early on ..or maybe an NG that went active...or as hard as it is to believe lol had a CO who just didn't like him...