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If you have a compass, wave your watch over the top of it and if the needle moves the watch is prob magnetised.
I have a demagnetiser - where are you based? (tho tbh they're cheap as chips on ebay and if your work means it might happen again you might want to pick one up)
[https://www.ebay.co.uk/itm/353453727403?hash=item524b7bdeab:g:XkMAAOSwQ3ZgdCTP]
Also this is quite a useful little vid - has CC to my knowledge [https://www.youtube.com/watch?v=IZ1RUrbyYuo
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I did just got a fairly powerful laptop recently (solid state drive tho).