Dear Bobj,

I have a 100% stock 1938 3/4 ton panel truck, and the seats in your pictures look very much like mine. They attach to the floor with brackets like those in your top picture (on the driver side). The holes on the back are, of course, not visible because everything was originally covered with a sort of leatherette. The passenger seat was an option, and mine, like yours, has slightly different mounting brackets from the driver side, but the dimensions are the same and should fit with the brackets on the floor.

So, it looks pretty much like you have original seats from a panel, ca. 1937-38. If you measure the distance between mounting brackets on the bottoms, I can check with mine to confirm that these would fit.

As you might imagine, original seats like these are rarer than rare--VERY difficult to find in any shape. I have no idea what they might be worth on today's market, but if someone is looking to restore a panel to original, these would be a very nice find.