The whole set up has the original company printing paper, and by the look of it the cupboard was used as a dark room. Stamped 1988.
How long till this is Antiques Roadshow appropriate?
One of my favourite routines about moving flats is going through all the weird shit people have left behind. Found this absolute belter of a "camera" in a cupboard (the whole thing, not just this manual) and I am buzzin oot ma boobies to figure it out.