The Hitachi HL-6312G is a index guided laser diode with multi-quantum well structure. It has a built in photo diode for monitoring the laser output for use in automatic power control (APC) circuits. The common case pin is laser diode anode and photo diode cathode.

Specifications:

Output Power: 5.0 mW typical, 6.0 mW maximum
Wavelength: 635 nm typical, 640 nm maximum, RED
Operating Voltage: 2.6 Volts typical
Threshold Current: 20 mA typical
Operating Current: 55 mA typical
Monitor Current: 0.4 mA typical
Operating Temperature: -10 to 50 deg.C
Package: TO-9, 9 mm diameter base

A factory spec sheet can be found HERE

Note: Due to the sensitive nature of laser diodes, there is no warranty or exchanges on these items.