Omega Seamaster PRO GMT (2535.80.00) Revisited (Update #3)

After the first two updates (both in this post), I got along fairly well with the SMP. It got put into my regular rotation and it was fairly accurate (~+2s/d). However, I noticed two things: (1) The GMT hand would sometimes get stuck at 8am. And (2) the GMT wheel did not click from hour to hour when I was quick-setting it.

Another minor issue was, that the crown seemed to be on the way out. It required a deft touch if I wanted to wind the watch, otherwise it would slip.The dealbreaker was the GMT hand.

I figured I would need to open it up again to sort the hand. I did not yet know what the problem was, but I thought that either the hand was loose or that the dial opening was uneven.

While I would have it open I would do some more maintenance – I bought a genuine crown a while ago, but it did not fit the tube in the rep (it has the screw on the inside, not out as is the case here). I also ordered a genuine tube, but I was worried that the opening on the case would not fit. The diameter could be wrong. I recently procured a push-fit crown removal tool, but I did not know whether the crown tube was push-fit or screw-in. Both of them exist in Seamasters. I therefore decided to test this on a backup SMP GMT rep case I have, to see how to do it, before inflicting it on a watch I am actually using. If i then borked the case I use, then I could always use the  backup case. I did not want to immediately use this one, for two reasons:

  1. Because the thread in the back is not sealing perfectly – it is water-resistant to 60m (with the new crown), but still, it bugs me that I cannot screw it tight.
  2. The case-back itself (more on that in a second).

I followed the excellent Archer’s guide on how to remove the crown and everything proceeded without a hitch. I used an aftermarket Clarks crown and tube (I know this is advertised as genuine, but it isn’t really. It is, though, half the price of the genuine crown and tube).

When I got the crown out it became apparent why the backup case was not watertight previously (the crown tube hole was malformed). It was also too big for the tube I had. I used marine epoxy, put a thin film around the crown and pressed it into place. Waited 24 hours, repressed the crystal, lubbed everything, sealed as far as I could and then tested it. It passed! But the only case-back that fits that case does not have a display window. If I borked up the case that I use currently, this one would work, however it would not be ideal. The 2535.80.00 has a display back (as indeed the case I currently use, does).

In the meantime, I also bought a genuine bezel with blue insert. Here is a comparison photo between bad rep, passable rep and genuine.

As you can see the replica and genuine inserts are subtly different, especially at the lume pip. The genuine insert has an additional steel circle around the pip. Note that omega does not sell the bezel and the bezel insert separately, so the ring needs to be replaced too. The replica bezel works on a spring wire, or with a little pip on a spring. The genuine has an insert with a raised piece of metal that works as a clicker. Below you see the three bezel backs. The middle one is genuine, the left and right ones are replicas.


I left this issue to one side for the moment, since I needed to completely disassemble the case anyway.

One suggestion put forward in the guide linked above is to put the case into boiling water in order to loosen the Loctite securing the crown tube in place. In order to do this, you need to remove all the gaskets (the one in the back and the one between the case and crystal). You also need to remove the bezel and insert, and the crown, obviously (because there is a rubber gasket in the crown itself). You also need to remove the bracelet, because the springbars have springs inside and the whole thing will get destroyed by the boiling water.

I proceeded with dissasembly. And removed everything from the midcase.

I boiled it for about 10 minutes, dried it off.

And then pushed the crown tube out without much difficulty. Note to self – the SMP cases, especially the GMT case, need to be put on the machine crystal side in, otherwise, they slip and break the pusher (I have now ordered several spare pushers:) ).


When I put the crown tube in, it did not fit perfectly, there was a bit of space between the case and the tube. Not much, perhaps 0.1mm, and it might be solved with loctite, but I would never be sure about its resistance to water ingress. Therefore, I mixed a bit more marine epoxy and pushed the crown into place. I now had to wait 24 hours for the epoxy to dry.

Therefore I could turn to the movement. I replaced the GMT wheel, so I got the click back. I replaced the datewheel for the hell of it and used a diamond file to smoothen the edges of the dial opening. I also put just a dab of loctite on the GMT hand once I had it perfectly in place.

I reassembled the movement and left it running outside the case, to let Loctite dry (with many of these cemicals and glues, I am worried that the fumes in  a watertight space (like closed watch) will stick around and slowly erode the hands, dial and movement). The other reason I left it outside of the case was that I wanted to see whether there was an issue with the hand clearances (a lot easier to reposition the hands while they are stil outside the case).

While I was at it, I also replaced the stem, because the existing one looks to have been previously damaged by the pliers. Not strictly necessary, but since I had everything out, I might as well do it.

While I was waiting for the tube to dry, I lubbed the gaskets and re-pressed the crystal. Note to self – How happy am I now that I previously bought the crystal gasket replacement(s)? I am very happy :).

I cleaned the crystal and re-visited the bezel issue.

Genuine used insert (before cleaning)

The genuine (After)


I do have the bezel assembly of the genuine case, but the rep case hole is only big enough for the spring wire, not for the little steel pole that might work here. Hmm… will need to sort it out. There are a few options:

  1. Drill a hole in the case and insert the steel pip (like Rolex has them). The hole dimensions are Diameter: 1.6mm, Depth: ~3.3mm.
  2. Buy a genuine disk spring. Does not apply for this particular midcase because it does not have a drilled path for the disc.
  3. Replace the insert only. While I was taking off the genuine bezel to drill a hole ( I had it on, but it was not flush with the crystal, so I removed it again), the bezel insert fell out of the genuine disc. So, 3 it is.

Here are the two solutions rep cases employ, on the left and right there is a hole and a spring wire (above the left watch case). The middle case has a larger hole and the pip and spring.

While I was at it, I realised that the genuine insert is just a bit too tight for the crystal. I needed to uniformly enlarge it, just a tad. So I did.

Once the case is ready and the tube to dry, then I’ll need to lube the bezel assembly and press it into place. Everything else is ready for reassembly as soon as the epoxy in the tube dries (I protect the hole in the tube with rodico/watchmakers putty).

A day passes. I re-visit the GMT.

The movement has cheerfully worked through the night. No need to do anything with it. I oiled the stem with (Moebius Synth 9415 lube).

The tube is firmly epoxied in place and is not movable at all.

I lubbed the back gasket and the crown gasket with silicon lube and tested the closed case for water-resistance. I did the proper test where I left the case under pressure for at least ten minutes and only then submerged it and released the valve.

The case passes without any issues. 60M WR. I would be happy to even go diving with it, but will for sure use it for snorkelling.

I set the bezel, glue the insert into place with a few dabs of gorilla glue (there are some adhesive strips available for bezel inserts, but they often don’t do a god job in my experience).

I reassemble the watch, and admire it.

Genuine parts:
– Dial
– Hands (except the GMT hand)
– Crown
– Crown tube
– Bezel insert

Rep parts
– crystal
– case and bezel ring (I have the gen ring, just wasn’t able to use it).
– movement and datewheel
– Bracelet and clasp

I add the steel bracelet, set the watch and put it on my wrist, where it is right now.



3 thoughts on “Omega Seamaster PRO GMT (2535.80.00) Revisited (Update #3)”

  1. my respect to this great and detailed watch that it has even reached me to germany in the south black forest celebrity 😉
    I own a omega 007, which was broken after an accident, the demanding housing, including bezel. then obviously the ex-owner has a new housing request part can be adapted from the mark mark & ​​sons the 007 clock cover and the dial are still original and I can not say with certainty whether the clockwork was not defective after the accident and also swapped. My problem now is that I want to put the clock back to its original state or a decent and reasonable omega state but I do not have a suitable fore housing now I am also a disease-related retirees and my budget leaves much to be desired
    my question to you / you specialists would be how I should proceed here and which housing would offer part of the pictures here pictures of the clock I deliver at the beginning of the week when I’m back home

    1. Hi dude,
      If you want original housing you will have to pay for it, I am sorry to say. The chances of people replacing housing as a part of a regular service are vanishingly small, so it is not likely that you would be able to get a used replacement part from an omega service boutique. You could look on eBay for a broken watch and buy that, but it is likely that that would cost you more than just buying new case. These cases are often restricted, but even if you find one that isn’t expect to pay about 1000EUR for it. That is just the midcase, to be clear. The back, the seals, the crystal, the crown, the crown tube etc have to be bought separately. Some of this could be reused from your previous watch, for sure. The mechanism appears every once in a while on specialist sites. But that will also cost you non-trivial amounts of money. If I was you, I would have it repaired, if it is genuine Omega. That would be cheaper than buying NOS mechanism.
      Take the watch to the Omega boutique, explain what happened and ask for the watch to be assessed. Then ask for a quote. If the watch is a replica, they might seize it, but then you wouldn’t lose much money. Unless you bought it as gen, then you need to chat with the ex-owner and get your money back. A good 007 rep is what, $350? So if you are happy with a replica, buy another.

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