Updated: Jun 1, 2021
It is often said that "Necessity is the Mother of Invention". My view is that Simplicity, coupled with Creativity, is often the Mother of the Best Invention! It was clear that if I was going to get this invention "off the ground" I had to "home in" on one design of case, because retro-fitting a prism in the case was a much cheaper alternative to manufacturing the lid part of the case with the prism in it; the injection moulding tool would have been very expensive.
So, since there were so many different designs of audio cassette case, I located a supplier of one design of case, and had 5000 prisms made. I then fitted these to the lid part of each case. I developed a repetitive strain injury due to having to break the sprues off each prism (a sprue is the piece of plastic protruding from the prism after it leaves the injection mould). I then built a small rig to clean off the remainder of the sprue; washed and dried the lids, and fitted each lid to the other part of the case.
My daughter's Dance Teacher purchased some of the Prismatic Cassette Cases from me, and found then useful for identifying her cassettes whilst they were stored in a suitable larger case; like a brief case. She did not have to use the inlay cards and just read the titles via the prisms.