The OL-1 was also used in RK05 control panels and in the KA10 CPU front panel.

The OL-2 was also used in 5408458 peripheral indicator panels.

The TU56 control panel uses part number 12-09637.  These are described as 
"Lamp, Pilot #3590A20 Line-o-lite".  They are apparently 12VDC indicator 
assemblies (with the white box and frosted panel) made by Industrial 
Devices, Inc.

Need lifespan data for the various bulbs!

Apply derating formulae to the CM7370, CM7371:
CM7371: 12V, 40ma, .12MSCP 10Khours vs 10V, 40ma, .05MSCP, 5Khours
CM7370: 18V, 40ma, .15MSCP 10Khours vs 15V, 40ma, .075MSCP 50Khours

CM7371 derated: 10V, (10/12)^.55*40ma, (10/12)^3.5*.12MSCP, 8.9X life
              : 10V, 36ma, .06MSCP, 89K hours
CM7370 derated: 15V, .9*40ma, .53*.15MSCP, 8.9X life
              : 15V, 36ma, .08MSCP, 89K hours

Brightness tolerance is generally 25%, 7371 is 20% too bright, 7370 is 6%.

CM7371 substitution works well according to Bill Maddox.