The ETA caliber 2893-2 is part of the Mecaline Specialities line of ETA movements. This caliber is available in different grades and can be supplied by ETA with a Chronometer rating. The 2893-2 is very similar to the ETA 2892-A2 except that it has a modular GMT complication. Official ETA tech sheets were found dated as far back as 2002, showing that this movement has been in production for at least that long. The example in the photos is from a Sinn 857 S UTC.
Setting the GMT Hand:
The GMT hand sets independently. Unscrew crown and pull to position I, turning forward/clockwise will adjust the GMT hand by one hour increments. Turning the crown backwards/counter-clockwise will adjust the date. This is very convenient because you can adjust the GMT hand without hacking (stopping) the movement. For GMTs that require hacking the movement to adjust the GMT hand, it also requires readjusting the time.
Caliber Number Location:
On genuine ETA 2893-2 movements, the caliber number is located on the plate beneath the balance wheel. The ETA shield logo is also present. To the left is an origin/date code with a sequence of letters and numbers. On the example movement pictured here the code is: V8DJ6. The V8 code indicates that the movement was produced in Switzerland.