Old hard drives are good sources of strong rare earth magnets.

[sjrapid]

...and these are the magnets removed, but still attached to their mountings.

Thanks mddock58, that's exactly the type of hint I was hoping for. I've disembowelled a number of drivers over the years, (I've got a stack of old platters in my office at work) but I've never gone after the magnets before.

Best regards

[mddock58]

Magnetic "information" CAN be changed by magnetic fields realigning the "data" on whatever it is on. the biggest danger to credit cards and such are the "Security" demagnitizers at stores ( so you don't walk off with a CD or DVD) which have a strong rapidly changing field.

Generally a magnet will not cause a problem with most items, but a magnet in a pocket or sporran freely moving about may cause data loss. It is not a simple "this will, and that won't". Caution in the size and strength of a magnet should always be considered.

Using them to keep a kilt pin on should not cause any worry, unless there is a metal plate in your leg!