Well, far more complex than I'd imagined.
The slides are all from the '70s and, at the time, some of them were quite good. What 35 years of being stuck in a cupboard has done...
Oh well, I'll look out for a second-hand one and have a play. There's no serious use for the images - might construct a calendar form some, perhaps post some to a hill-walking forum if they're relevant. Certainly not going to get obsessive about it.
I've bookmarked this topic so that I have it for reference when I get a suitable tuit.
Thanks to all who have helped me.