It was first issued in 1948 and knowing how slow the military acquisition process is, it would have been designed and specified several years earlier. I intentionally didn't go with the straight plain lettering because that's how the original is and I wanted to avoid comments that I was even copying the lettering.
Interestingly, the first ones didn't have the blunt hour hand, this was introduced following requests from RAF pilots who reported difficulty in differentiating between the hour and minute hand.
Eddie