I've a 203mm Ektar in Flash Supermatic. At the bottom there is the bit you unscrew to slide the lever between an F setting (F printed in black) and a red M setting, then you retighten it. Other shutters give you the option of a black M or a red M, depending on which shutter speed range you're using. The shutter speeds on this shutter are red up to 1/10th, and black from 1/25th on up. Does this red M apply to all shutter speeds? Does the 'neutral' position (i.e. screw positioned at center) have a function (e.g. is it for the black shutter speeds) or is it just an 'off' setting?

The red shutter speeds are for the red M only and the black for the black, this is due to the differnt peak times of the flash bulbs. I'm not knowledgable about the center position of the lever.

Have you reviewed the posts in the following link?
https://www.graflex.org/helpboard/viewtopic.php?topic=2099&forum=12&23

Just to clarify, there is no black 'M' setting, only red, as well as the black 'F.' I should add that you have to cock a timing mechanism lever to set the flash sync. Also, there is no solenoid on this shutter. So to simplify the question, will the black shutter speeds work with this red M setting?

Incidentally, in referencd to the thread Greg suggested, I seem to recall hooking up an electronic flash to this shutter (with switch in 'neutral' position--i.e. neither F nor M selected) and getting a properly-exposed image.

Thanks for the help!