The origin of these was the battery of lenses producing 4, 8 or more simultaneous identical images on a single large plate. The contact printed positive was cut-up to provide images for family and friends. These were simple lens without diaphragms and barrel thread mounts - gem lenses.

The next step was a large camera, again with a large plate, but with a single lens. An ingeneous, and often patented, mechanical system moved the plate holder through vertical and horizontal to fill out the plate with lots of variations of the same portrait sitter.

By the way, these tiny lenses did have the locket trade in mind.
I quote from the Ross Catalogue in CCHarrison's website.

"A Portrait lens producing with the whole aperture pictures of a size for Locket plates 1 1/2 x 1 inch and with the diaphragm size 3 1/4 x 2 3/4 inches. 6.
A set of WH diaphragms in morocco case for ditto. 1."