Here is an amazing and beautiful Vintage Hickok 6000 Mutual Conductance 12AX7 KT88 amplifier tube tester checker. It has the socket adapter plate, and it comes with a test data manual! Several sample tubes (6L6, 12AX7) were tested, and it seems to work well! This has been stored in a climate-controlled place for decades. (I'm sure it would benefit from a light cleaning and maybe a calibration.)
A rare and wonderful addition to any collection of vintage electronics! *See Photos*