Hi all, A friend of mine has the watch below. I told him it at 35mm or so doesn't suit his wrist as he's a fit individual with thicker wrists and this mid size is more in keeping with what ladies are wearing these days. He also has a Link 43mm which suits him perfectly and he's after a Cal 1887 black titanium just like the one I've posted here. What I need help with to assist him is: 1. What is the S90 code on the back? Doesn't look like a serial number. I thought this was a W code watch base on the article on the Cal 11 website. 2. What could he expect to sell it for? It's in pretty good condition, probably 8/10.