What is a Graflex SPEED - I - O - SCOPE?

I did an internet search for Speed-i-o-scope and found some post to the old helpboard, hoping to find a definitive answer. Alas the only post that sounded credible turned out to be one of mine!
I did find one of these on ebay and the seller generously scanned the instructions and sent them to me.
So for the record, These were used in Tachistoscopic learning or contolled flash projection. While the one's I've seen were too knew to be used by GI's for learning to spot enemy planes, the effect is the same.
For people on this list old enough to remember her, I'll bet Evelyn Wood bought a lot of these.

It really is nothing more than a shutter. If you have the Speedi Sr. then you have an iris too, the Jr version did have this feature. So go buy a nice Golden Dagor in barrel and ship them both to Steve Grimes with some money and you'll get back a sweeheart of a lens.