Cyma chronograph clamshell

Known as the first waterproof chronograph wristwatch, the distinct "Clamshell" case was patented in 1936 by Schmitz Freres & Co. It's a unique two-part compression case with a specialized flared crystal. The

"Clamshell" case is also easily recognizable by the presence of four screws on the reverse side of the case, located under each lug.

The whole design was aimed at increasing the water resistance of the case.

So many manufacturers took advantage of this patent, including Cyma.

This oversize chronograph best represents the mechanical and stylistic ingenuity of the 1940s/50s.

The condition, diameter, and timeless look make it a desirable piece for any collector