Hi,

I've seen it refered to as

"Shutter focal plane, rotating slit, gives 1/250 s, 1/125 s, 1/60s, 1/8 s, 1/4 s and 1/2 s"

If you haven't seen Alfred's Page, you're missing lot's of insight and opinion too.

http://cameras.alfredklomp.com/horizon202/index.htm

If it's not on Alfred's page, it hasn't been written!