The ref 2777 was produced for the RAF and issued for only 1 year - 1953. Three versions of dials can be found on the 53 RAF Omega. The first version was supplied from Omega to MoD with Radium on the dials. These were called the "Thin Arrow". At some point the MoD figures out that Radium on the dials is a problem and they decide to change this. They go ahead and redial the watches themselves. This was done by hand and thus we have a redialed watch called the "fat arrow". This is the example in the image above. When these watches started appearing at Bienne for restoration, Omega made a limited run of new replacement dials, which had the “Thin Arrow” again. The watch itself is made of a thick metal case with a soft iron internal shell surrounding the movement (cal. 283) to protect the watch from magnetic fields. According to Omega only 5900 units of this watch were ever produced.