This is a newly built TM500 power module tester / utility power supply plug-in: originally built by Tektronix but not available anymore, redesigned in 2021 by NFM (Near Far Media), who gave open access to the design.
This plug-in tests the +/- 33.5V DC, +12V DC and AC supply of the power module, plus the NPN and PNP pass transistors. Besides, it can be used as a utility power supply plug in, with +5V DC 1A, and +/-15V DC >400mA with overcurrent protection.
You find further information, including a video teaching application of the plug-in, by following the links on the Tekwiki site on the 067-1201-99. 
This is a newly built plug in as redesigned by NFM, with some modifications to increase the ruggedness of this unit: built using meachanical parts of 500 series plug-ins, with aluminium frontplate, additional rear plate, larger power resistors.
The plug-in is tested for all functions and burnt in.
Please allow for up to 4 weeks construction and testing time.
Postage worldwide is included.