I found this old military jacket the other day - I've never found one like it before. What era is it from and who would have worn it?

by whereismyshoe

So I found this jacket at a thrift store today and it's unlike anything else military that I've found. No tags besides a small "S" on the inside of the collar. It's clearly a work jacket of some sort, but I have no idea why it's yellow - who would have worn one of these? It has donut buttons with "US Marines" embossed on them. Any help would be greatly appreciated, it's really a cool piece and I want to know more about it.

Pictures here

butter_milk

/r/military might be able to help you.