One not need to have even worked on old computer systems. I'm not even retired yet, and I've gone to the library to look stuff up in old newspapers that were on microfiche. When I was a mechanic back in the day, parts listings were on "fish", too.

I think the author read "microfilm" and instead of hearing a synonym for the thing car parts are listed on, I'd bet the immediate thought was little micro spy cameras to put your microfilm in.