From my Sylvania Dealer catalog.
Sylvania M-3 Flashbulb
Synchronization: Ideal for both class M shutters and simple box cameras.
Rapid initial rise and relatively flat output characteristics meet
requirements of most late model focal plane cameras.
Light output: clear 16,000 lumen seconds, Blue 10,000 lumen seconds.
Peaks at 17 milliseconds. A medium range lamp.
Base: Miniature pinless: Miniature adapter fits it to midget base reflectors.
Reflector: For maximum light output, use a 3" polished reflector

Francis in VT