Cool. thanks guys. It is a leaf shutter and a newer one so it does have a PC sync. Time to look for a suitable flash. SOmething from the same period would be cool
Well, you probably won't trigger a nuclear counterstrike with them, but you might well run into problems from the EPA for your disruption of the circadian cycles of wildlife in the surrounding counties...
I'm not 100% sure I'm remembering this right, but I believe the Press 40's are actually the same brightness as the Press 25's, the only difference being that 25's are a midget based bulb, and the 40's screw based (aka Edison base, or Mazda based) bulbs. The Press 25's are also the same brightness as the #5's, and if you check the graflex.org website, there's a whole section on flashbulbs there, and they have a guide number chart for #5's online there, which should be either the same, or pretty close to the Press 40's.
Actually, I'm pretty sure the #5 and P25 are both bayonet bulbs, as opposed to the ring groove "midget" base M2, M3, and M5 sizes. M5 and #5 have the same light output, different bases. P25 is a bit brighter than #5, guide numbers differ by about 10% as I recall.
Never seen a P40, but if it's a screw base same brightness as P25, that would explain the screw base flash with bayonet adapter that came with my Ansco Pioneer 620...