Some games are rare, others are scarce. Production numbers can be misleading. I've seen many more copies of "Neptune" than "Gemini", but perhaps because I'm in an add-a-ball state bordered by another add-a-ball state. Distribution and survival rates determine how often a particular title will turn up. I would think at least half of the number of any late '70s EM title would still exist today, but for some reason, certain titles seem to come up far less frequently than others with similar production numbers.