Thank-you kindly, gentlemen. I found it, just where you said.
In perfect time for winter film lab test hibernation. When it's too dark to shoot, you can always slosh.
Now I wonder if Rollei still makes a TLR in which to use it.
Did I ever tell you about the college student who did a scientific study of the navel height of 1940's photojournalists, based upon optical analysis of the pictures they made with their Rolleis?