But what is identical? For example, here is the list of HPL lamps and its a long one:
Wattage Voltage Lamp Life (in hours) Output (in lumens)
375 115 300 10,540
375 115 1000 8,000
550 77 300 16,170
550 77 2000 12,160
575 115 300 16,520
575 115 2000 12,360
575 120 300 16,520
575 120 2000 12,360
575 230 400 14,900
575 230 2000 11,780
575 240 400 14,900
575 240 2000 11,780
750 77 300 22,950
750 115 300 21,900
750 115 1500 16,400
750 120 300 21,900
750 120 2000 16,400
750 230 300 19,750
750 230 1500 15,600
750 240 300 19,750
750 240 1500 15,600
Now, with all the above, color temperature for standard life 77-120v lamps is 3250K, 230-240v standard lamps is 3200K, and all lamps long life is 3050K. All the lamps look exactly the same (minus a slightly different filament between some) and use the exact same T-6 base.
So lots of options. The difference between all them in the fixture was is first, you won't find 230-240 watt lamps here because everything here is 120v and the wiring is thinner gauge due to less amps needed. Second, the 77v lamps are for double dimming. Beyond that, you can pick and choose to your heart's content. The major difference however is that most fixtures (Source Fours) are rated to handle up to 750w lamps, the Pocket Scans are not however.
But I did give you a way to cheat some more power out of them. The problem is I don't know how long the lamp will last running with 20% more voltage then it is rated to handle. It might very well burn out instantly. The 115V to 120V is a much smaller increase, 4.3%. But doing that also shortens the lamp life again. The 8v is a 50% increase which I am positive it won't handle at all.
In movers, I almost always change lamps for different color temperatures I want, namely MSD 250/2 for MSD 250 since they are exactly the same minus the fact that the 250/2 has a color temperature of 8500K and the 250 has a color temperature of 6700K. I prefer the lower color temperature because it is more true to white and colors like ambers, oranges, and reds come out better. However, here is a HUGE disclaimer: DO NOT MIX/USE DIFFERENT SPEC ARC LAMPS IN WRONG APPLICATIONS, YOU CAN AND WILL CAUSE SEROUS DAMAGE AND POSSIBLY INJURY.