Unusual item if you happen to be looking for one. It's the portion of the Polaris finder for a CG-4 or CG-5 mount that actually threads into the mount. It has three set screws and the rubber o-ring used to hold and adjust the "finder." It was already on my CG-4 mount, but when I bought a new finder, it came with it. I'll be amazed if anybody wants or needs this thing, but I hate to throw it in the trash.
Make me an offer. Would trade for a really cheap, old 1.25" erect-image diagonal if you happen to have one laying around.