How easy is it to magnetise a watch ?

[Burlington]

Not strictly a Rolex query as it relates to my AP diver - but figured the watchtech sub-forum was the right place. A few days ago I put the dial side of my diver very close to a magnet (quite by accident as it was embedded in a piece of equipment and I inadvertently held my wrist briefly against it)

It would have been close enough to have been within the magnetic field, but as of yet I see zero evidence that the watch has been magnetised.

I gather the ROO line has a built in anti magnetic inner case but just how well does this type of design shield the movement?

Curious how this may compare to something like a Milgauss which is specially designed for magnetic fields.

As a more general query - Anything else other than major deviations on timekeeping which may show a watch is magnetised ?

Could running a known to be magnetised watch cause unseen damage to the movement ?