Hello. OK, so I recently acquired a large archive collection of late 1960s tv/celebrity glass slides (in German metal Cenei covers). At first I assumed that there would be two pieces of glass and a piece of celluloid/film sandwiched in between. A few were broken and I also opened a couple of them. The good quality positive photo images each appeared to be on one of the two pieces of glass - which was mysterious as the glass surfaces were/are wholly smooth. No signs of any emulsion. I was baffled - and so were the various people/experts that I contacted/badgered via Google. Today I went through the collection again and there was another broken one (of Cliff Richard) - but this one shows how they were made. The photographic images are on very thin transparent sheets and are somehow stuck down so well that they end up feeling like they are part of the glass itself. My question is, how did they create the thin plastic sheets with the photos on them? Has anyone come across this kind of thing before? I have attached some pics to make things clearer - one pic of a Harry Seacombe intact piece of glass, and the other is the broken Cliff Richard one. All info welcome!