Hey, amazing news! I bought a tool.
It was the 30-odd pieces of black plastic and an assortment of screws and springs.
And it actually works. I put a test roll of film through it and got it developed yesterday in my local independent camera shop (Pause for a moment and dwell on the excitement that there is a local independent camera shop. Actually there are two. Amazing.) They all came out, all in focus, and no light leakage. Really pretty impressive, and bags of character. (That's code for "tiny area actually in focus" and "dark corners/vignetting") My previous camera use has been purely means to an end stuff; this is more "Have camera, what can I photograph?" Different experience entirely, and seeing the familiar through the reverse image viewfinder adds a Through The Looking-Glass aspect too. All in all a fascinating thing. Ridiculously satisfying too, especially making the shutter work. click click click click click
The scanner elected to make them a little redder than they should be, but you get the gist. The double exposure was unintended - although I did plan to try one anyway, albeit not quite like that... You know those Easter Island heads? Look at that sundial and tell me you don't see their extremely flat-headed cousins.