Hot-swap drive has magnetized rails??

We were looking at a 4 year old hard drive with rails and has an hot-swap
enclosure that it sits in; it plugs into the IBM RS/6000 B50 server.

When the hot-swap modular unit was disassembled, it was discovered that its
rails were magnetized.

What we are curious about is if... this is typical of IBM pSeries / RS/6000
servers' internal hot-swap disks' rails? Or even if it's common with other
make/models of hot-swap hard drives with rails?

We think it's odd that rails would be magnetized, considering the media in
the sealed drives are themselves also magnetized.

We're wondering if this was normal, expected, or if it was some form of
transferred magnetism to the drive rails over time?

-Dan