Jeff Huber is right. The thick case...
I contacted Omega long ago and according to them the case is thicker because of 1. the valjoux chronograph movement. 2. the thicker case is because of the extra components around the push buttons for water-proofness. As sources (omega in Penn, and Chronos mag) tell me it is the ability of the chronograph to be used underwater safely without seeping in. The push button guards have small o-rings that can be changed for maintenance without opening the case. This is what Omega has told me. Best wishes, Louis PS, I have that model and it does work underwater safely....right Jeff? :-) Great watch!! To me it is the most practical watch made. I was told it is the only water proof chronograph watch. Enjoy!
: According to my Omega pamphlet, the Seamaster Chrono 7750 movement (Omega
: Caliber 1164) has 25 jewels and white rhodium plating. I am uncertain why
: it is considerably thicker than other 7750 chronographs. Certainly its
: 300m water resistance must be a factor, and its unique design that allows
: the chrono buttons to function underwater may also contribute to its size.
: Jeff