I've just done some research, and Energizer and Duracell alkaline batteries were freely available in 1985.
EverReady changed its name to Energizer in 1980. The batteries we have today would have looked very similar to the batteries from 1985, and would have been alkaline (although the older technology was still available).
The bike lights that I was using in 2006 before upgrading to LED lights looked near identical in design to the ones that were available in the 1980's. And the ones I was using in 2006 were more than adequate for any type of cycling. The biggest problem was that the connecters went dodgy after a while. That has never happened with LED lights.
Even I was thinking about lights from the 50's and 60's in my initial comment (and maybe earlier), even though I wasn't born then. I don't know why I thought lights were so basic in the 80's. They weren't.
So anyway, in 1985 it was possible to go into Halfords and buy high quality lights for a bike for an affordable price, that could also be very safely used today.
Some of my touring friends still use the Dynamo, mainly because it charges it self and they dont have to carry chargers for them, a little bit weighty though, i think the problem with the ever ready battery was, it didn't last long and the bulb wasn't bright. I have the Moon lights and Halfords own brand light 1800 lumens, i bought this one so i can charge my phone from it while out camping, the LEDS changed and advanced cycle lights.
