Clearly some kind of clamping device. When you turn the handle it would grab something in the other end but I have no clue what it might be used for. Some kind of cable clamp maybe ? Kinda reminds me in a way of the panel clamps used in auto body work for pulling bent metal but I see no place to attatch a chain. What type of work does the shop do that your brother works at ?
I agree that it looks like its meant to clamp onto a cable or other cylindrical material...seems like a very specialized application. I love this game!
I'm thinking if it were used near water it would be rustier. The aero dynamics but heavy cast construction indicate it may have had to plough it's way though something so maybe an adjustable part off a plough or other farm implement.
Its design is of the early 50's or earlier.
Without seeing the under side I would think it was a hold down clamp for a machine. I doubt it is for pulling cable and it is not a stretecher. I think it is apart of something else.