What is this baseplate compatible with?

Hello!
This is the baseplate on my Cambo 4x5 monorail. What is it and what type of tripod head would I need to grab the whole plate? As of now, I'm just screwing into the threaded hole with the screw on my tripod (an old Bogen/Manfrotto).

Thanks very much

It's a manfrotto quick release plate I believe. I have a three axis manfrotto head somewhere that takes this plate.

+1 on Bogen/Manfrotto quick release.

gotcha thanks- I think I found it!

I'd reccomend the 3047 3-way head. It uses that hex plate and is strong enough to hold a 4x5 monorail.

As the others have said, that is a Manfrotto / Bogen hexagonal QR plate. Most of these plates mount to the camera with a thumbscrew, but you have the variant that mounts to the camera with the large flathead screw in the middle. You can unscrew that with a screwdriver, and then mount your tripod directly to the camera.

The Manfrotto/Bogen 3047 3-way pan head is a good though heavy head that takes the QR plate and can support a monorail. There was also a ball head that took the hex plate, though I don't think ball heads and monorails are a great mix. Until you get a matching head, I think it will be more secure if you remove the plate and screw the tripod to the camera.

The small screw heads in the plate are setscrews used for an anti-twist feature.