"SUPER PITCH PIPE" guitar tuning device

This little thing is sorta along the lines of the various other musical instrument tuners I've shown recently (and the harmonicas too, for that matter) in its purpose anyways, if not quite in 'form'. A "SUPER PITCH-PIPE" made by "WM. KRATT CO. U.S.A.", it is their "SN-10 SP. GUITAR" tuner. In its original (though broken in several places, all the pieces are still there) plastic box, it is about 2-1/2" wide. In function it is similar to a harmonica (with brass reeds inside) except that it only plays 6 particular notes corresponding to the proper tuning of guitar strings instead of any kind of complete musical scale -- the guitar player could blow each one in turn as a reference to tune the individual strings of his instrument.

Guessing it is 1970's vintage, leastways from slightly before the time when everybody had a "cell phone app" to do the same thing instead...? I found it (and saved it from the trash) a decade or so ago amongst the detrius while helping friends clean out a rent house.