For Sale FS: Pentax 6x7 Mystery Adapter/Extension Tube

[Ari]

I bought this thinking it was a #2 extension tube for Pentax 67.
It certainly accepts Pentax 67 lenses, but the camera side of this adapter doesn't fit the Pentax 67. It looks like a P67 mount, but it's a couple mm smaller.
What camera does it fit? I don't know since I have only a fixed-lens digital camera, a Mamiya RZ67 and a 4x5 here with which to test.
It clearly says "Pentax 6x7" and there's also a "2" on the other side of the tube, but again, it's a mystery as to which camera it will fit. Maybe a Pentax 645?
If you know, please post here.
Meantime, I'm offering this for $20.00 USD shipped to anywhere in North America; overseas at cost.

 

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[JBrunner]

Looks to be an adapter to mount 67 lenses on a different system, the camera side looks too large to me to be for the Pentax 645 tho.

 

[Ari]

Too large for the P645? Here are some photos of the outer diameter of the ring on the camera side. Diameter is 2.5565" or 64.99mm
Pentax 67 lenses fit perfectly on the other side.
Thanks for your input.