SMTD995
Tektronix part number 152-0140-01 is a 10 mA (+/- 1 pF) tunnel diode with a maximum capacitance of 8 pF.
It is used in the 547 units with serial numbers 11890 and up.
According to Craig Sawyers' Diode Reference, it is used in the RM546, RM547, RM585, R544, R556, R7912, S-51, S-52, TU-5, 067-0572-00, 067-0572-01, 067-0681-00, 1S1, 1S2, 1502, 21A, 22A, 3T5, 3T6, 475/R, 475A/R, 475M, 544, 546, 547, 556, 581A, 585A, 7B52, 7B53N, 7B70, 7B71, 7D10, 7D11, 7T11, and 7T11A.