The Military version of the Submariner ref. 5513 was adapted following the specifications requested by the British Ministry of Defence. The watches had to be fitted with fixed bar lugs with a diameter of at least 2 mm. The dials had to be easily readable and were therefore equipped with the larger "sword" hands. They also had to show the international symbol for Tritium, the encircled "T". The hack feature allowing the precise setting of the time was another specific request. The models furthermore had a unique bezel with sixty minute marks rather than only the first fifteen minutes. The outside of the case backs were marked with the military broad arrow sign, Ministry of Defence issue numbers and unit number. Furthermore the inside of the case backs repeated the serial number which is commonly only found between the lugs.
The outside of the case back of the present watch is engraved with the following markings:
0552 for British Ministry of Defence, 923-7697 for the NATO code, the Broad Arrow characterising all watches owned by the British Army, the issue number 444 and issue year 76.
The serial number to the inside of the present case back reads 3'826'414, leading to the assumption that the back has most probably been inadvertently exchanged against the original one during a servicing.