I was pretty excited to find a box full of these handmade slides at the flea market this weekend--a box in which many were rolled up in newspaper from 1945, seemingly untouched since then!
What I've learned is that Carl W. Lange Sr. and Jr. , who copyrighted this set of stereoscopic slides in 1942, were father and son opthomologists with a practice near St. Louis and a particular commitment to curing myopia (nearsightedness.) They wrote and travelled extensively promoting the "Visual Training Technique," which these slides (the complete set was known as "the Coordinator") were used to facilitate, all with the objective of re-training myopic eyes to see correctly. As one slide (in my listed "Set 2") reads: "It hardly seems fair to start people on a lifetime of glasses if their sight can be corrected by orthoptic training."
It seems from some research there are a few partial sets like this out there but I can't believe there were very many made as it would have been quite a laborious process: weighing nearly half a pound each, they are composed to two panes of glass, with black & white copied images framed with black paper overlays (all hand-cut), typed classificiations/descriptions at right, printed squares with copyright info on reverse, and then red tape around the edges.
I've sorted through and lightly cleaned all of them, weeding out some in poor condition, and divided them into 5 sets of 8, organized mostly formally. Overall, they are in good shape and show well, but I think they were stored in a basement for some time where there was some moisture as there is a little mildew here and there showing against the black paper inside the slides, and some scattered staining to the red tape. Detail photos provide a good sense.
Each slide measures 8 x 3 1/2" x 3/16". Sold as a set of 8, exactly the slides pictured here.