The earlier production tools I find at the flea markets seem good quality; e.g. "dyna-ring" impact sockets, wrenches marked "proto professional" etc.; the sockets in particular, seem really well made IMHO; the stuff I am running into is probably pre 1980's however.
Proto "Dyna-Ring" impact sockets; they came out in 1960: mine I think are 70s vintage
Proto "pear head" design ratchet
Proto "professional" wrenches
Proto "500" series highly polished wrenches
I am not a fan of the design of their ratchets but many here like them; the "pear head" style has been around forever.
There are brand linkages to Plomb (the name used before 1948 as a result of this trademark dispute, Plomb was required to change the brand name marked on their tools, and chose "PROTO" (from "PROfessional TOols") as the new name)and Blackhawk, Challenger; so keep your eyes open for them as well. I like the fact that people don't recognize the brand, the definition of a "sleeper" tool and can be bought typically for next to nothing; at least in my areas flea markets/pawn shops. Just keep your eyes open for newer era tools as many of the "Blackhawk" branded tools are made in Taiwan.