Having seen Carl Radfort's pictures today of the skull they reminded me of work I did 10 years ago. This involved creating an image from double exposure within the camera when slide copying. The hit or miss aspect came when you had to wind on the shutter without allowing the film to move.
I remember seeing these images you created in camera when you did a talk in Clondalkin some years back, Nice to see one again. You should put a few more up I am sure they will be appreciated by APUG members.