Kind of a poor-man's Octo Finissimo 😀
Twice the thickness (10.3mm as I measured) but a fraction of the cost.
(and twelve-sided, not eight)
And perfectly synchronized, quite a feat with a non-hacking movement!
From my limited understanding, the Zodiac inroduced the separating spine in the hand around 1962 or 1963. I think it was during or after this period the hackset was introduced too. I'm guessing your SW features a 699 movement, seeing SWISS is printed below 6 o’clock. Is yours rated for 10 ATM or 20 ATM on the caseback?