LB re your #46.
i remember preparing OHP slides using Lumicolour “F” fibre tip pens. Make a spellin mistake and start again.
we had red, blue and black celluloid tapes of various thicknesses used for laying up printed circuit boards. Twice scale against a grid on a light box. These could be used for straight lines or tables. Also had various sheets of coloured film which could be cut to size and stuck on with a bit of spit. This would have been in 90s before computers were common place.
i remember being asked to go go to Cranwell to deliver a presentation to EOT. Take your Power Point on 3.5 Floppy discs and a set of back up slides printed on A4 film just in case the projector fails.