No idea either. I guess you don't know if it's even complete?

I have one of those!

To be more accurate I have all the parts to make one that looks identical.

I have a collection of about twenty steel straps, bars and plates with a mixture threaded, clearance and slotted holes that are an adjunct to my lathe and milling machine. Used for holding work to the table, lashing up jigs and all manner of tasks.

The parts in your picture may just be how someone left then last time they were used. I cannot see it being a specific piece of equipment.

Ian P

It’s a very good example of what I try to avoid when making anything. Having to have a whole bunch of different tools to make adjustments because I didn’t use the same size fasteners! I built something quite complex using a lot of different parts many years ago and gave this a good deal of thought. Whilst I had to use M3, M4, M5 and M8 bolts, all the stuff that might need adjustment used M5 cap head socket screws.