Justlearning,
The 3600 would indicate it's a 3/4 ton. The quickest other way (for a novice) to know would be a 3/4 ton should have a longer bed, and three stake pockets. The 1/2 ton would only 2.
That is of course unless someone has gone to alot of trouble and shortened the frame and change the bed.
There are a few other ways to confirm, but that should give you a solid idea of what you've got there.
Your boyfriend sounds like an awful lucky fellow.
