despite being a vetern of the Vietnam era. 
 
You could say that Frank's platoon was secretly tested on for what became SHIELD's Infinity Formula. Thus why Frank Castle's not aged much since. *shrugs* Food for thought.

which universe are you referring to.

Punisher's origin is retconned to the next war. Last I remember reading he was a marine during Desert Storm. Also the Infinity Formula was around during WW2 so there was no need to test it. Although giving Frank the Infinity Formula would explain a lot about the character and how he gets out of serious injury.

" Punisher's origin is retconned to the next war. Last I remember reading he was a marine during Desert Storm. Also the Infinity Formula was around during WW2 so there was no need to test it. Although giving Frank the Infinity Formula would explain a lot about the character and how he gets out of serious injury. "

I am trying to remember the issue it was in but I am pretty sure he was talking to another marine and they were standing around in the desert. It could have been a Marvel Knights Punisher but I am not 100%, but I am almost 100% certain the 616 version's origin has been retconned to explain why he doesn't look old. Also it only makes sense they constantly retcon origins to bring them more into the modern times. Just look at Stark he started out a captive by Viet cong working with Mandarian, then it was Desert Storm, and now its Afghanistan.