What does 6x6 in Lens board go to? (~ 153mm)

I have this 6x6 in lens board. Metal. I dont know what it belongs to.
Soon to find it's home though I hope!

Attachment 155918 Attachment 155919

Possibly to an old copy camera? I think I have an un-drilled 6X6" grey wooden lens board still in it's envelope (to rainy to go out to the shop and check). When I was a USAF photographer many years ago we had an 11X14 copy camera, a huge beast of a camera...I think made or marketed by Calumet. It may have used 6X6 lens boards but I can't remember.

thanks for the guess Randy.

I wonder if anyone recognizes the lettering as typical of any manufacturers?

Is that for the Calumet C-1 8x10? Looks familiar but it's a while since I used one.

6x6 lens boards fit 8x10 Empire States, Kodak 2's and 2D's, B&J 8x10's and Rembrandt 5x7's, and probably a few others I don't recall off the top of my head...

Well wait a minute - my F&S 8X10 takes 6X6 lens-boards...