Maybe they focus the "old guy" rays I give off, but so do I. I have a small collection of slide rules, all normal sized linear types, which I still am fascinated with. They're all made between the 1940s and 1960s and aren't terribly rare but the care and precision that went into their manufacture is amazing given that they weren't terribly expensive back in the day. I especially like the one's made of bamboo. Not as much precision nor speed as a calculator or computer but always remember that we got to the moon on them.