Recently, Casio has started manufacturing DW-6900 G-Shocks with a new 3230 module inside (the module is the brains of the watch, including the LCD and all functions). The DW-6900 watches have had the 1289 module installed in them since their debut in 1995. The old 1289 only keeps track of the correct date until 2039. The 3230 module goes all the way up to the year 2099. It's likely that the venerable 1289 will be slowly phased out in the coming months or years. 16 years so far has been a good long run for this technology.
Take a look at the photos below to see the different case back designs. This is the easiest way to tell these watches apart.
Original DW-6900MS "Made in Thailand" with 1289 module (photo by Sjors)
First "Made in China" DW-6900MS with 1289 module (photo by strongergodzilla)
New DW-6900MS with 3230 module (photo by matley)
Casio also moved the manufacturing of many DW-6900 models from Thailand to China. And along with this change of production facilities came a new case back design that takes its inspiration from older G-Shocks, like the classic DW-5600C that came out in 1987. There are still some DW-6900 models made in Thailand, so maybe the ones made in China are simply overflow in demand that the Thailand factory cannot meet. Some of the most popular G-Shocks, like the DW-6900MS, are the ones that lately seem to be coming from China.
Classic DW-5600C case back with module 901 from 1987
Fwupow has made this video that compares the modules
SOURCE : New 3230 Module vs. Classic 1289 Module: Update for DW-6900 G-Shocks
Thank's Riley for the post...
