What is this?

[Jonathan]

I got this at an auction in a box of more useful bits. Looks interesting but I can't think what it's for. When the handle is turned the taper is pushed via a the thread again all the bearings, so they're pushed out. Maybe it's some sort of clamping or measuring device? Although doesn't explain why it's all solid copper! It's inscribed with 1" X 1.25" and a patent number which I can't quite read unfortunately.