Butler cup but you're missing the ring the cup sits in.This mount is/was on my 2001 'wing when I bought it. What is it supposed to be for and if anyone knows the maker, perhaps I can find what things mount to it.
"Folded" and "unfolded" pics...
Thanks for the heads up about the (non) reuse of the longer mounting screws. I think a Ram mount for a GPS will be in the plan eventually. Most of my riding (passenger or not) involves enough stops to stay hydrated and we have plenty of cooler and container options.You will need the OEM screws/bolts when you take that off. While not "needed" it would be nice to have the plastic cap that snaps over the socket head screws once installed. Usually when I reinstall this cap I add a dab of my favorite glue to help keep it in place.
Alternatively, you could replace this with one of the RAM ball mounts. This comes with new screws and would allow you to add a mount for a phone, GPS, radar detector, fishing rod holder, pistol holster, etc.
There are other third party accessories that also mount using these screws. Not a big deal, your choice, just can't reuse those screws so you need something in advance.
BTW: Nice looking rig. Unless you use a Camelback type water carrier, you should keep hydrated and a cup holder of some type is a good idea.