hmm...In your place, I would still inspect the other stuff that came with it, if you still have them (you did say they were rusted out). If they threw it all into boxes randomly before the auction...probably was not so random that related tools wouldn't wind up in the same box. That is just a by product of smart packing. You keep a box with you throw everything near you into it until the box is filled, then grab another box. If it was sitting on something next to things used with it, those things probably went into the same box.
Maybe it is a key of some kind? maybe one or more of those machines had a drive slot on a bolt head that was cut in at an angle so as to fit that tool, and required a lot of torque to tighten down and loosen up. One might hold the knob bearing down while turning the handle to tighten a strangely slotted bolt in place or to break it loose. I have seen freeze plugs that require tools that are stranger still so it wouldn't surprise me.
