They don't actually make the stuff.... they sold rebrands originally manufactured by a variety of companies. There was a time that Sears (and their famous catalog) were one of the biggest resellers in the U.S... hence... the rebrands. You also have to know the time period we are talkin about. It was a time that Chinese products were cheap and crap. It was a time that Japanese products had serious quality issues. (Some Japanese cameras/lenses had those gold stickers that indicated that it was inspected prior to export.) The American named products were the biggest and strongest names associated with quality. Again.. this drove rebranding under American names such as Sears, Heiland, and Honeywell.
I do know early on, many of their cameras were made by Asahi Optical of Japan (eventually spawns Pentax) but rebranded as "Tower" cameras. I have a few of those in my collection.
I believe Mamiya, Olympus, and a handful of Japanese products were rebranded to American "Sears". I have a few M42 "Sears" in my possession as well.
Boy have times changed....
Side note.. I haven't found proof but I have a feeling my home (built circa 1925) was also a "Sears" home. They sold everything in those catalogs!!