First off, I like your avatar. Those Willys Wagons are way cool.
OK, about your knife...does it have an insignia or shield or any kind of logo on the flip side? Without a little more information to work with, it may be hard to ID. Just like today's pocket knives, there were similar shapes and sizes made by various manufacturers in the old days. It looks too rusty and cruddy to open up, so we'll have to base our guesses on what the other side looks like, and the number of brads holding the handle in place. Also, sometimes the backside or the all metal side (opposite the side where the blade would open) gives clues.
I like digging up old pocket knives. You know some real guy was there doing something. And you gotta know he was ticked off when he realized he had misplaced his knife!!!!