It came without a second hand, but I managed to find one to fit. The colour match is good, maybe its a tiny bit too short.
The case is a one piece job. Its marked as 20 micron gold plated - which is a shame as some of these are solid gold.
And the back is marked Waterproof, Seastar Seven, Use Key No. 295T.
Anyway, I assumed it was a split stem arrangement and give the crown a firm tug - but nothing. Just as well I didn't pull harder, I think, as I believe the casing/movement arrangement could be similar to this automatic one I found on Roland Ranfft's site:
in which he helpfully warns:
"..attention: no detachable stem; the dial can be pulled off to allow unlocking the stem from the front side."
So no movement shots just yet!