+1
But, I have to say am very impressed with the "late model (2009 up)" DG3804. There is a good chance this is what you will get with a "21J" Cartel GMT, GMTII if it has been made in the last 2 years.
Late Model DG3804 PROS:
No overlay needed. Correct Datewheel spacing for GEN dials.
Font on datewheel is good enough.
Correct hand stack for 6542/1675 and slower 21.6 bph
GMT function is a small step above modded 2836's
These new movements seem to have good Quality Control. Two I have, are clean and properly lubed.
Will fit in GEN 1675 case or Yuki/NDT/Phong case with easy mod to Yuki/Stilty adapter ring. Correct stem alignment.
Late Model DG3804 CONS:
Incorrect hand stack for GMT II 16610's (So is the 2836)
Slow beat if used for GMT II
Rotor winds one way, so you occasionally can hear rotor whirl.
To summarize, if you are going vintage GMT, I find it hard not to justify a DG3804. If you are going modern GMTII, the increased bph 28.8 of the modded 2836 might be a better fit.
This is a DG3804 with a stock ETA 2836 datewheel on top demonstrating the reason why all 2836 based Rolexes need an overlay.
DG3804 Top side (GMT gear/pinion not shown)
Superior Datewheel mechanisim. Aligns with all GEN dials, MBW dials, I have placed on top of it.
Below is a Ronin Build powered by a DG3804 movement. Keeping excellent time +6 seconds per day. 42 hour reserve.