S.K. Grimes, Inc - nice surprise!
S.K. Grimes,Inc. advertises on their website various lens flanges and retainer rings (nuts). You know these are two different parts - one fits on the front of the lensboard to be attached by screws, and the other on the back and works as a nut (jam nut) screw-in fit.
I ordered a retainer ring (nut) and to my pleasant surprise found that Grimes delivered their proprietary design that was _both_!
REVISION - stilly me - Grimes might have simply shipped me the wrong part - a flange, rather than retaining nut.
We will see.
Damn, I'm stupid. REALLY Stupid! (I wish I could delete the whole thread, but for some reason it is not an option now.)