The TD1081 is a germanium tunnel diode with a peak current of 50 mA and a capacitance of 6 pF.
Tek part number 152-0099-00 refers to the diode itself. It is used in the 017-0086-00 pulse generator.
Tek part number 152-0334-00 is the same diode mounted on a metal clip. This is used in the delayed pulse generator (D992) of the 661 starting with serial number 271.