I was looking for other watch parts and remembered I had put a box away with misc parts years ago. Imagine my surprise when I found this Cyma Watersport three register chronograph in the bottom of the box. I'm not sure, but I think I bought it 25 years ago. It had a broken stem and I had put it away with the idea of getting it repaired at a later date. Well, I guess this qualifies as a later date! Works perfectly. At it's heart beats a Valjoux 71. It has a heavy thick clamshell case. Glad I found it!