Recently, I've noticed that my black dial Seamaster GMT has been running on the slow side.  In monitoring it over the past few weeks, I've noted that it's starting to slip outside of COSC standards - sometimes as slow as 6 seconds per day.  It's almost 4 yrs. old, and could probably stand to be serviced by Omega.  However, I decided to try my hand at regulating the watch myself.  It's well outside the warranty period, so there's no harm in my opening the case.  I don't dive with this watch, so I won't worry about changing the O ring (which should be done once a year to maintain the watches maximum water resistance). 

My Seamaster GMT has the Omega caliber 1128 inside - based on an ETA 2892-A2.  I've had good success doing a self-regulation on an ETA 2824 (found in my Invicta 9937 and 9938) so I at least I've got the benefit of some experience.  However, the biggest stumbling block is the case back of the Seamaster - it requires a special case opener.  My first step is to order a set of Omega Seamaster case back openers from the Timezone Tool Shop for $70.00 delivered.  The price is high, but I figure if all goes well, I'll save myself that much on a the regulation of one Seamaster, let alone future regulations on the 3 other Seasmasters I own.  Here's the tools:

  I was initially pretty ticked at having to buy pay so much to open the case back, but after getting the tools, I really appreciate their design.  The first step is to remove the Seamaster bracelet.  Then, put the watch case in the matching black case holder from the above picture.  Here is a picture of my Seamaster in the case holder - it holds the case very snugly, and really minimizes the chance that the case will get scratched while removing the case back:

Next, simply mount the red "key" (they include one for the men's models, and one for the ladies models) onto the case back by matching up the five points of the key, to the corresponding five holes on the case back.  This system works REALLY well.  It's VERY easy to scratch a case non-Omega case back with a generic case opener, but the Omega design really makes the process virtually "idiot proof."  Here's a close up picture of the key:

It looks as though a ratchet could be used in the center of the key to gain additional torque.  However, I found it very easy to just hold the black case mount in my left hand, and twist the red key in my right - much like opening a jar of peanut butter.  Here's a picture of the inside of the case back, and inside of the case with the case back removed:

The first stage was complete - I had the case back removed.  I then encountered the anti-magnetic cover over the movement.  It popped off easily enough using a jewelers screwdriver wedged under a corner.  I now had my first unobstructed view of the Omega caliber 1128 - it took my breath away!

I took full advantage of this rare treat and took many pictures of the movement.  The pictures came out quite well, but they don't do the movement justice.  I was floored by the beauty of the finishing applied to this movement.  Evidence of the quality workmanship was everywhere!

The timing screw is visible in the above picture (it's right above the words "Twenty-Three" in the above picture, right in the center of the piece that looks like an upside down 'Y').  I simply used a jewelers screwdriver to turn the screw two notches toward the "+" sign, which should speed up the watch by about 10 seconds (each hatch mark should be good for about a 5 second change).  Once done, I reassembled the anti-magnetic cover, and the case back.  I then synchronized the watch to the atomic clock, so I can observe the accuracy over the next 24 hrs.  If I'm right, my Seamaster GMT should now be running about 2-4 seconds fast per day, which would be about as accurate as I can get it with the tools I have available.  The whole process took me about 30 minutes, but minus the picture taking time, I'm sure I could do it all again in about 15 minutes.