That's probably where it's pulling the keys from for LUKS/FDE - you'll have to get the keys off at some point to decrypt that hard drive, though I'm not sure if plugging it into a regular PC is a good idea. Would be nice to find some more info on that first!
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Looks like it's one of LaCiE's USB keys. While I can't find that exact one, the
petitekey and
iamakey look pretty similar - so it's almost certainly a normal USB drive. I'd also put a roughly 99% chance of it either being formatted for Linux or encrypted using the private/public software the manuals keep talking about. I'll have to defer to the Windows nerds on how you can image an entire drive (not just one partition) in a way that's not gonna modify the drive itself, but with any luck it'll have the keys to decrypt the PC's hard drive on it.