very interesting ^ !
I cannot add anything to this very in-depth dissertation, but as for
"American Cyclerly in San Francisco which closed some years ago."
not true.
There were once two locations but now just one on the SW corner of Stanyan and Frederick, very much still in business.
The other location (on SE corner, a former Schwinn dealership) did close many years (decades) ago.
They both used the same name: American Cyclery. Maybe they had some designation (shop #1, shop #2?) but IIRC you went into one and if they didn't have or do what you needed they sent you across the street.