The DW-5600C (left), compared to the newer DW-5600E.
My 5600-C is a Japan "A" model with module 901, the 5600E is Malaysian made with the 1545 module
Superficially they are very similar. The main difference is the protective ridges on the bezel of the 5600-E.
The tradition screw back of the steel-cased 5600C compared to the 5600E's screw-plate back. The 5600C is a considerably heavier watch. I find the 5600E more comfortable to wear and have the strap a notch snugger than the 5600C. On the wrist, the older model has the feel of a classical dive watch on a rubber strap.
Side view. The "set" button on the DW-5600C is smaller than the other buttons.
As some of the button functions were changed for the 1545 module, changing watches can be a little irritating! The EL backlight on the 1545 is far superior to the old "lightbulb" in the 901 module. It is a pity Casio dropped the handy REM feature for the useless "AUTO-EL" in the 1545. The dual-time feature was also dropped completely in the 1545.
(I apologise for the irritating reflections in the last pic.)
Hope you enjoyed!