Share 'Lantern slide or 35mm slide transparency?'

Hello  I'm seeking some advice around terminology. I've come across a few 35mm colour slide transparencies sandwiched between two pieces of glass and taped - from the 1950s. Has anybody seen anything like this before, and if so - would you call them lantern slides or just slide transparencies (mounted in glass or encapsulated in glass etc)?  Best wishes Nicola