Here are some other references for further information and confusion:
Ecklers, 1949-54

Ecklers, 1955-62

Chevs of the 40s, rope and rubber

Bob Adler

Best Gasket, Rope and Rubber

I have some 261s that I will be rebuilding over the next few years. I'm not sure what I will do. I might try the conversion to the one-piece seal that was discussed a few months ago. https://www.stovebolt.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=687066#Post687066

Hoyt