Melles Griot model number 05-LPM-915-065
This is a new, old stock power supply  that will operate a typical 17 to 20 inch long HeNe laser head.

Specifications:

Input Voltage:   115 / 230 VAC, 50 to 400 Hz.
Output Voltage:  3100 to 3700 VDC.
Output Current:  5.5 to 7.0 mA user adjustable. Preset at 6.5 mA
Trigger Voltage: >12 KV
Input Leads:      12″, 22 AWG. Flying.
Output Leads:    12″, Alden high voltage connector.
CDRH delay:       4 seconds. (Defeatable by cutting violet wire loop)
Dimensions:       7″ X 2.4″ X 1.4″ (178 x 61 x 36 mm)
Mounting holes: 0.15″ diameter x 3, 2.95″ x 1.8″ center spacing.
Warranty:           30 days from date of purchase.