It's very likely that this was done post-factory. In those days, you could purchase internal lights and install them yourself. Of course, factories did custom orders but this seems more like some drummer who was sick of soggy calf skin and bought himself a box full of lights. Very cool drum!

I'll bet the thought behind positioning a light at every tension point was to maintain perfectly even tensioning all around the circumference of the head. A single lightbulb fixture, as in John's newly acquired BB, would keep the whole calfskin warm and tight, but I'll bet the portion of the head directly above the bulb gets super warm and tighter than the rest of the head, resulting in uneven tuning. Just my guess. Anyone else?

I'm not a scientist so I don't know for sure, but your theory makes complete logical sense. Spock would be envious!

'V' Live Long And Prosper!

John