I'm assuming this is for the rear of the truck. Doesn't look right to me. Should be a crown the length of the fender. The front of the fender should have a flat that extends out slightly to meet the running board (Sim to your '37). Also the inside mounting flange doesn't look like it would fit the high and low panels of the side of the box. FYI the '38 through '41 1/2T rear fenders are the same.
Hard to tell for sure from the photos but its possible that somebody who didn't know what they were doing tried to learn metal working and totally screwed it up. Maybe somebody will recognize what its from. Some of the early Chevy trucks looked very sim.
If you look at Mart's video you will get a good look as he removes his rear fender @ 4:50 into the flick.
https://www.youtube.com/watch?v=5Cn-...ature=youtu.be