Why do you get to find all the good stuff?!?! It's not fair! It's probably better that you find them than me anyway, though.. The fact that you've found a super rare fuel truck is one thing but the fact that you've found an original Marine Corps truck is even better
The fonts in the Marine Corps were not standardized as far as I know. But that looks like a 40's/50's stencil font if I had to guess. Marine Corps registration #'s were 5-6 digits long during WW2. They are all six digit now.
However, due to the fact that you've got that semi gloss forest green interior I would say that it is a post-war paint job - probably Korean era if I had to guess.
If I had to guess, I'd say that the tanker was probably on an MCAS or NAS somewhere due to that yellow paint job. My CCKW K-53 is the same (faded) color. And if you would like to compare paint chips I would be glad to as I'm going to have to get this paint mixed up custom anyway.
This tanker is great and all and I know Bill already has one but I am going to go and check out a rumored Quickway Crane about 90mi away either tommorow or next weekend. If it really exists and is in restorable condition, then I think we'll all be even.
Brian