I received a camera for Christmas from relatives. It came with a single M2B flashbulb inside a sleeve for 12-bulbs (used for padding during shipping). The carton was marked GTE Sylvania, Drummondville, Que. and “made in Canada” although I don’t know if that refers to the carton or the bulbs.
All clear flashbulbs were also available with a blue coating for colour slide films. In the days of flashbulbs you could buy three-sided flash shrouds: they had a clear, a blue tinted and a diffuse side. Such covers were recommended for extra safety in case a bulb blew up, firing glass at the subject. All flashbulbs were coated with lacquer to prevent glass from shattering, but there was a slight fear if the coating was scratched the glass would get loose.
It seems M2B flashbulbs were made for use in three-inch polished reflectors. If used in matt shallow reflectors one stop more exposure is recommended. It is also assumed the matt/shallow reflectors are used inside rooms with walls to reflect some of the spilled light. If used outside an extra stop of exposure is recommended. Curiously if the M2B flashbulb is used outside with the three-inch polished reflector no correction is needed.
You can get “M” base bulbs in various powers. The M2 is about as strong as an AG-1 bulb and both are at the low end of power. The M5/M/25 were more powerful while the M3 was much more powerful. Later flash cubes were very powerful, yet far less bulky. There were many flashbulbs made with Edison base’s (like lightbulbs). Some were so powerful they were used during night aerial photography. Then there were the infrared bulbs…
So much of using flashbulbs revolved around the shutter and the sync. Focal plane shutters worked well with “FP” sync flashbulbs and because of the FP bulbs long peak output you had a choice of higher shutter speeds.
“M” peak flashbulbs worked best with “M” sync. The bulb was fired 12-20 milliseconds before the shutter opened so the flashbulb had a chance to get up to full burn. You can use “X” sync (were the bulb fires as soon as the shutter is open—no lead-up time) at 25 sec.
Gas filled bulbs were a third kind of flashbulb you almost never hear about. They were the electronic flash of their day giving 200 sec equivalent exposure. They were not particularly powerful. They seemed meant for box camera people who wanted to try stopping sport’s activities within a 10-foot range.
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