Just received this today - if you can't afford the extortionate rates for a new core holder on the UK, and don't want to wait the week or more to get one from Japan this does the trick!
To clarify - this is a way to get a cheap adapter to put your own watch strap on the smartwatch 3! I am not advocating having the watch core dangling from your bag to be stolen!
Received today and the keychain part is attached by a clip and velcro strap - undo these and you're left with a core holder for your smartwatch 3 and pins attached - ideal to put your own 24mm strap on and for much, much less than buying a similar on eBay.
Happy customizing, SW3 owners!