Here's my entry: Ref. 01 0010 500, powered by an ESA 9162 tuning fork movement (Zenith calls it 50.0). Some design elements are clearly taken from Zenith's Surf/Defy line: the back states surf and the bracelet is very similar to defy divers. Though, this very piece seems more rare - or let's just say it's an oddball in Zenith's 1970s line up. Very elegant and massive watch though, and if I am not mistaken an integrated bracelet design that came out long before the Nautilus and perhaps even a tad before the Royal Oak .. Anyways, if anyone knows more about this watch, perhaps years of production and such, please let me know. I can't seem to find any vintage catalogue from around 1970.