These Variable Capacitors Work -- Ether or No Ether!

Amazing that the arguments about the presence or absence of a luminiferous ether made its way into parts advertisements in a radio magazine.  This is from Radio for January 1923.  (About 18 months before my dad was born.) 

BTW that capacitor looks very nice, and would almost certainly still work.  I have caps like that in my junk box.   The shape of the blades helps address one of Pete Juliano's complaints about analog oscillators -- the inconsistent spacing of frequencies on the dial. 

Thanks to the K9YA Telegram for posting this.