Um, Polyglot, would you by any chance have a bakelite-bodied Brownie Hawkeye? I ask because that was my first camera and until I learned how the shutter worked I got unexpected and sometimes surprising double exposures with it.
This because pushing the shutter release lever down fired the shutter and pulling it up also fired the shutter. I think the wikipidia entry bvy directed to us misrepresents how those shutters function.
More seriously, the simple shutters being discussed are a kind of guillotine shutter. Sector shutters have been used in a few still cameras (Univex Mercury, Olympus Pen F) but are nearly the norm for cine cameras. The Agiflite, an aerial camera that shot 6x6 on 70 mm film and is essentially a cine camera with a low framing rate, has a rotary sector shutter whose top speed is 1/2000.