The Tektronix 013-0100-0X is a TO-3 transistor adapter for curve tracers.
This P/N maybe be re-configured in the "+Regulator" version. There is a new label included from the factory, along with the instructions for internal wiring modifications. Refer to the second page of the Datasheet (PDF) for the modification instructions and the new label placement. It is almost a different adapter, sort of two for the price of one.