I’ve got a 12” Eastman Ektar, which I believe is the same lens but uncoated. It’s in an unreliable ilex shutter but the optics work. I’m not certain if the rear group would work with a coated front group, but if you want to try I’d be happy to sell it
Thanks:
The diameter of the thread of the rear element is 66mm. It is a Commercial Ektar.
Your lens is an earlier version and , quite good, even though it is uncoated.
I do not think it will fit but you can measure it to see.
Also, yours is probably a different design altogether.
Check it anyway.