old musical instrument tuners #1: PETERSON model 400 STROBE TUNER

Introduced to the professional music public in 1967, the PETERSON model 400 STROBE TUNER (and its derivative models in immediately following years) quickly became an "industry standard" tuning device widely used throughout the entire music industry -- literally everything+ from 'in people's living rooms to tune the piano' to 'the high school bandroom' to 'onstage with Jimi Hendrix/Bruce Springsteen/Pink Floyd/many, many others'. Also key to the ultimate success of these machines, they were the first "solid-state" strobe tuners...thus inherently more portable/durable/stable than any other such device of the time.

In operation, the ASTATIC microphone (shown clipped inside of the removable lid to the tuner along with its power cord) is plugged into the front of it, which would then 'hear' the pitch of the musical note being tuned. The sorta triangular window on its front is illuminated from behind and shows what is in fact a 'spinning disc'...the marks seen on it are calibrated and turn into little 'bars' which appear to be rotating slightly sideways (one way or the other) to indicate whether the note being tuned is "sharp" or "flat" until the note is "in tune", when the 'bar' quits moving. The various knobs and controls allow adjustments of which note is being tuned as well as general "pitch" adjustments of the entire machine.

It was manufactured by PETERSON ELECTRO-MUSICAL PRODUCTS (then) of Worth, IL, a firm which is very much still in business to this day. I don't know offhand exactly how old this specific machine is (if I called Peterson in the morning I'd bet somebody would be able to tell me?) but its probably on the sorta 'early production' end of things.

https://en.wikipedia.org/wiki/Peterson_Electro-Musical_Products

It is in a black tolex (I think that's the generic name for the stuff guitar amps and such are covered with isn't it...a textured black plastic-ish coating anyway which is quite durable) box, measuring about 9" x 11" x 5".