1962 Gibson Guitars and Amplifiers Catalog, Page 23: GA-5, GA-6, and GA-18T >> Vintage Guitar and Bass
My mid-1960's Gibson Explorer GA-18 tweed tube amp, with built-in tube tremolo. Bought this from a friend in 1992-ish for $75. Works perfectly. Sounds great. We call it the "ibSon". : r/GuitarAmps