I've already found an addition to this thread. In the April 1969 Ballcard Collector, from which I posted above the "Martin Opens His Mail" column with a letter from Mastro praising the paper, also has a "For Sale" ad by Mastro, which I've posted below. (See below the "Card Collecting on the West Coast" article, which I'm about to post in another thread.) In fact, I assume that Mastro's letter of praise for The Ballcard Collector accompanied his ad when he sent it in.
