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AnthonyBesides The Trader Speaks, and before SCD there was Sports Collectors News (SCN). Also The Sport Hobbyist, and the Ballcard Collector. But these were all early '70's, long after Burdicks time.
In SoCal we had monthly card club meetings in Orange County, as well as the annual convention in Anaheim that would draw dealers and collectors from around the country.
I think there was also a directory of collectors that was started in the '50's, and somewhere I've got a catalog from the late '60's (either Bruce Yaro or Richard Gelman's) that offered the updated list. Gar Miller's book also had a listing of prominent collectors.
It's certainly a lot easier these days though- on any given day ebay can have 2 examples of a card you might have waited years to see back then.