It is a old school reed FRAHM TACHOMETER . I haven't seen one in over 20 years. But today I got my hands on one (for free) to keep. The outside cast of it has seen better days, and there is a small crack in the glass. But I'm not complaining. It seems to work perfect. Absolutely no batteries. It is just a musical instrument.
Nice, I have an old treysit sirometer around here somewhere, similar principle; would love to have one of them.
