From the time when dinosaurs roamed the earth wearing their 1960s Heuers:
Late 1976 and we are going to announce and demonstrate to the press version 1.0 of our full 3D CAD system in a fancy hotel in London. At the time software was 99.8% transported on 1/2" tape (networks did exist but were mainly incompatible with each other), and the borrowed large filing cabinet-sized computer had no tape-drive. It did have a removable disc-drive though -- holding a magnificent 3Mb. I, as installer and demonstrator, had to take the disc and the tape to the computer manufacturer's UK base 20 miles away and transfer tape to disc.
The cost of transport was going to come out of what I actually had in my wallet on that day and I certainly did not have enough to take a taxi, so the London Underground it would have to be (think T in Boston, Metro in Paris, Subway in NYC, etc). Snag with that was that the scuttlebutt opinion was was the magnetic fields from the motors on the trains would corrupt any tapes or discs exposed to them. Nevertheless I took the magnetic media, did the transfer, took them back, and found they were uncorrupted, so the announcement and demonstration went OK. (I have skipped a number of other problems, if you want to know more I'll tell you over a beer, although might take three....)
At no time did I think that what could affect disc and tape could also magnetise my Carrera that I had been wearing for nearly seven years by then. Indeed as that was the start of my 12 years of intensive international travel still wearing the Carrera through airport scanners it still did not occur to me it might be a problem.
The Carrera? It's fine -- next week's watch in fact. Never been demagnetised. 42hours power reserve -- not bad for a Valjoux 7730!