I'm finally going through this big pile of stuff I got with my Crown Graphic 4x5, and along with the 3 cell Heiland flash (7" reflector) are two flashbulb adapters.

One adapter obviously fits the Press 25 bulb (as I have some that came with the camera) - a bayonet type adapter about 1/2 inch in diameter.

The other adapter I have no idea. It has the large screw base to fit into the Heiland synchronizer, and then it "adapts" to a screw base which appears to be about 3/8" in diameter. What sort of bulb is this for?

It doesn't fit any flash bulb, but at one time you could get a threaded candleabra (?) base bulb rated at 3 or 4.5 volts and was used to test the system without blowing a bulb.

They also still make these adapters for you house hold to convert edison base to candleabra base. but these usually look like bushings in that there is no tall section to raise the bulb higher.