The present reference 73663 is one of only two Heuer models, along with reference 741.603, to feature elongated Arabic numerals. Made for the Kenyan Air Force this may have been a special military specification for increased legibility in the dark. Produced in very small numbers, it is believed that no more than 250 examples were ever delivered with a small portion that were not issued. All of these models feature orange hands and indexes which in the case of the present watch have pleasingly aged to a light yellow color. If the difference in color is not obvious at first glance, a loupe reveals a noticeable difference between the paint used on the hands and indexes and the one used for the Arabic numerals. This unusual feature contrasts with the usual simple and easy to read designs used by Heuer for motor sport events and make this watch instantaneously recognizable by the Heuerist!