OK here's some properly C&V content

I bought a large slide collection from a garage sale. It was from the estate of a couple that ran the Photography club in Pasadena in the 50's. They both participated in photo competitions worldwide. The slides were sent in these custom boxes, designed to hold four glass slides.

They are held closed securely by this ingenious little strip of spring steel, which un-latches with pressure on the top and then pivots to allow the slides to be removed. Small paper holder with foam holds the 4 slides and fits snugly in the box

By evidence of the postal markings these were shipped to and from galleries and would be used multiple times

Patent # led me to the original patent application


https://patents.google.com/patent/US2797015