Mystery Solved: Rear Wheel Cylinders 65-69 vs. 70-75

"Sigh" I sure miss the days when we had REAL parts books that listed REAL specs. For about 15 years in 74 on I worked at two stores. The last was a big store. We had HUGE binders for Bendix, Raybestos, Wagner on brake parts alone. Back then you could EG look up individual cups and parts out of wheel cylinders and masters. And we carried a lot of them. You could "find out" stuff just by READING, and asking the "old guys." This store went into business (now long gone) in 31. "Old Nick" went to work there in 32. So when I showed up around ? 81, ? he'd worked there for 50 years.

We sold all kinds of stuff.
Full line of auto and light truck parts
Sold popular diesel parts like popular air brake components and tubing/ hose, and trailer shoes, turbos, popular injectors, etc.
We were factory dist. for Fafnier, Timken bearings, Wix filters, CR seals and Victor gaskets and seals and I don't know what else
We were dist for Browning drive products, sprockets, sheaves, and dist for Gates belts
We made hydraulic hoses by the hundreds, turned drums and rotors, changed axle bearings, relined truck and other brake shoes and winch bands
We had a completely separate Miller welder dealership and repair, and handled bottled gases
We sold chain and rigging, chokers, wire rope up through 1"
WE MADE a few pair of big industrial tire chains when we didn't have them. Stocked all kinds of tire chain parts, side chain, cross chain and hooks and latches
We were a dist for Proto tools and later SK and later, Armstrong
Before the boss retired, he started the town's first real dedicated Fastener's store