Method 1: have a secretarial pool type them all out each time
Method 2: if you were lucky enough to have a photocopier, keep the list on paper and photocopy them into labels. How do you delete someone? Whiteout that square. How do you add a new address? Find a recently blanked out square
By the way… in the 1980s nearly every company bought at least one PC. Why? To manage their customer mailing lists and print labels. It was a BFD when you consider how inefficient Method 1 and 2 were.
Fun fact: Reagan got elected promising to “run Government like a business” (meaning … efficient). After 12 years of Reagan/Bush, the Clinton administration was surprised to find the previous administration was using “Method 1”… not even Method 2!! Mr. “Run Government like a business” didn’t do the modernizing step that all video adds had done in those 12 years.