I first found these empty 35mm slide cases in 2017. Perutz was a German company that was taken over by Agfa in the 1960s. It has been presumed that they were a cargo loss, but no record exists of any. They seem only to be found on the North Kent coast.
After a beach combing session and sorting out, it just happened that some small finds fitted within the 'film' area. And so a project began which will be ongoing as and when I find more of these slide cases, and being able to pair the front and backs together.
It took some experimentation so that the slides could be picked up as you would normally, sorted into groups, displayed and kept in slide storage cases.