Metal fabricator here. The main bore through the middle sure looks like it has some remnants of threads in it, though that could be an illusion. The pointy protrusion says set screw to me, strongly. The pointy nature of the corrosion is odd on what assumably would’ve bean the meatiest part of the set screw, but maybe the head was twisted off, then the corrosion set in. The flat faced swollen area underneath the pointy thing looks classic for having female threads cut into it (to accomodate male threads on the shank of the pointy thing), or at least for the pointy thing to have been installed by press fit. The “handles” are interesting, are they both canted, the way a planes propeller is? If so, the photo makes them look like they’re both canted the same direction (very much unlike a propeller!). That I couldn’t explain.. but that could be an illusion. If they’re simply tapered, each like a straightened banana (or elongated football, sweet potato, etc), my guess is this is an adjustment handle. In that theory, this would have operated like a wing nut, threading up or down a threaded shaft, but in this case the function would’ve been increasing or decreasing the depth, tension, or spring pressure etc, on a threaded rod inside some kind of machine, the other end of the rod being affixed to a belt tensioner, spring plate, etc. Release the set screw, righty tighty to increase tension on the rod, lefty loosey to ease back, retighten the set screw once proper rod tension is achieved, now tension is fixed. Just a theory.
