Replica "faux" GMT movement FAQ & tutorial

[By-Tor]

G.M.T = Greenwich Mean Time

I decided to write this quick guide, because there still seems to be lots of confusion about the GMT movements. Besides the real GMT movement, like ETA 2893-2, there are three kinds of "faux" GMT movements in replicas, 2 based on ETA 2836-2, one based on Asian 21J movement.

The first one is the "correct hand stack" modification, which mimics the genuine GMT movement, i.e the "hour hand adjustable" watch. This modification has the GMT hand placed above the hour hand on the stack. The factories have developed this modification specifically for Rolexes, GMT Master II & Explorer II.

On this modification the date change follows the GMT hand, unlike the "wrong" hand stack modification, which makes the date change to follow the hour hand. (Technically the "wrong" hand stack version is just a standard ETA movement where the GMT hand has been attached to the main hour hand with a double sized rotor (that makes the full turn 2x slower.))

The "correct hand stack" modification acts like the real GMT movement, and it allows you to set the hour hand independently without stopping the seconds hand. When you set the crown into the 2nd position, only the hour hand moves in one hour jumps, while the GMT stays immobile. Like I said, there is no hack signal in the hour hand setup position, and the seconds hand keeps running.

Good example of a replica like this is the Explorer II ("correct hand stack model"), which I have reviewed HERE and HERE.

Below is a picture of the correct hand stack on my Explorer II:

However this modification might be unreliable, which is why I don't recommend it. Ziggy explains the potential technical problems with this modification in the RWiki section (avalable for RWG supporters only). The link is HERE.

There is also another "faux" GMT movement, which is widely used on replicas. It's the "wrong hand stack" 2836-2 version.

Replica snobs look this movement down their noses, because it doesn't act like the "real" GMT movement. In this modification it's not possible to set the hour hand independently at all, but you set the GMT hand instead. This happens when you unscrew the crown into date set position, and turn the crown anti-clockwise.

The problem with the GMT hand setup is that the GMT hand turns freely and smoothly over the dial, which (supposedly) makes it difficult to set the GMT hand "in sync" with the local time.

In my opinion, this is absolute nonsense. There's nothing difficult to make it sync with the hour hand. Just wait until time is say, 9'o'clock sharp, and move the GMT hand exactly into the desired xx:00 2nd timezone position.

When you have once set the GMT hand in sync, you don't necessarily have to touch it anymore, ever again (assuming you have a watch like Rolex GMT Master, which has rotating bezel with 2nd timezone hour markers). When you set the time (in the crown position 3) the GMT hand follows along perfectly (and stays in sync). If you want to set your GMT hand to follow some other timezone, you just turn the bezel into the desired position.

If you have a watch like "wrong hand stack" Rolex Explorer II (Exp II has a fixed bezel) or "Bond" Seamaster GMT, you have to manually make it "sync" again with the local time if you want to change the watch to follow another 2nd timezone.

It's also important to understand that the GMT hand takes 24 hours to make "full circle" on the dial. All GMT watches have separate markers for the GMT hand. For example on Rolex GMT Master, Black Omega Seamaster and Explorer II the hour markers for the GMT hand are on the bezel. These 24h markers are probably more natural to use for the Europeans, because it's the European way to tell time (24h system, not AM/PM 12h system).

The Asian 21J version of the "faux" GMT acts exactly the same way.

I have owned several "wrong hand stack" GMT's, and they have been bullet proof and reliable. There's absolutely no reason to avoid this movement. While it's not technically like the real GMT movement, it serves the exact same purpose perfectly and is completely functional as a "GMT watch". The purpose of a GMT watch is to follow the 2nd timezone, and this "poor man's modification" does it perfectly.

[perry563]

I have Josh's GMT Master II with the 2893 movement. (the one he sold for $428 but now unavailable) The question I have is as follows:

1) The GMT hand is set independently like the modified 2836 movements and the hand stack is wrong. Is this correct for this movement?

[ar0401]

I think the third existing 2836-2 GMT modification should be mentioned. In my PAM 063 (bought it from a member,

who in turn bought it from Davidsen) the 24 hr GMT hand can be adjusted exactly the way the 2893-2 works,

namely not continuously, but in discrete 1hr (or 0.5 hr if measured by 12hr scale) increments.

So far the movement works quite reliably.

[chrgod]

Great FAQ!

[jkerouac]

There are at least two 7750 watches with GMT hands -- a Breitling Navitimer, if I recall correctly, and the Chopard Mille Miglia GMT. I have the latter and so far it is rock solid. The GMT is set by putting the crown into date adjustment mode, then turning the crown in the opposite direction (similar to how you would set the day in day/date watches).

I have two other GMT watches, booth based on the 2836, a Seamaster Pro and a Pam. As By-Tor states, I first set the regular time on the hour, then set the GMT hand. I then go back and set the regular hour and minute hands to the correct time and the GMT hand tracks to the correct GMT time automatically. It isn't a big deal.

[eric3]

Hi,

I am a newbie so please bear with me, I have a copy Panerai Luminor GMT with the 24 hour hand and centre seconds it's a 029, i had an accident while looking inside and i now need a new movement. the one thats in it doesn't have any markings on so i was wandering where i can get a copy Asian movement.my wife bought it for me and she doesn't know i broke it yet and i want to keep it that way, the 24 hand is at the bottom of the stack and works as you say in your review turn crown one way to set the date the other way to set 24 hour, Please help.

Eric.

Edited February 18, 2008 by eric3