The other gold mine was having a hook at post office distribution center. An insider would grab cards( the enveloped were easy to spot) and sell them for 5-10% of the credit limit. Back in the day you didint have to activate from your home phone. Asking your mothers maiden name came later.
You happens to be 1000% correct, Lenox. Having a "hook" directly into a Post Office was a near perfect way for wise guys to operate credit card rackets. Because, not only could a "friendly" mailman swipe cards for them, but he also would make sure to grab the "follow up" letter the credit card companies would send out to their customers, advising them to call immediately if they hadn't received their new card in the mail yet.
