Who remembers these? Back in the 60's/70's I recall walking in to any drug store and/or hardware store and right inside was a tube testing machine. Solid State was in its infancy then and soon IC's and SCR's replaced/overtook the vacuum tube in circuits. Still can't beat the screaming sound of a vintage MARSHALL, FENDER, or VOX tube guitar amp though.
VINTAGE TUBE TESTING MACHINE: