A true “tool” watch for pilots, this is the automatic Citizen 51-1811. 

The inner rotating bezel (slide rule) is very useful for all types of calculations. The interesting thing about this watch is that it was used for its original purpose, as an aviator watch.

The case is really large at about 42 mm without the crowns. It is made entirely in stainless steel. The front surface of the case is brushed with a circular grain, and the rest is polished. There is an interesting blue light reflecting all the time from the brushed finish, giving it a satinated feel. The winding crown is located at 3 and the one at 2 is for adjusting the inner bezel. The crowns are not signed. The ring bezel holding the large, flat (35mm) mineral crystal is polished too. As pictured, the case integrates the lugs and the twin crowns, protecting them.

The dial is the main attraction of the watch. It is grey, with a sunburst effect. On the outside there is a golden ring with black digits. The golden ring is circled by a thin red zone delimitating the dial from the golden rotating bezel. The entire face of the watch is shiny and powerful. On the grey zone there is the applied Citizen logo, the white painted lettering “automatic 21 jewels”, the day and the date (sharing a single golden frame) and the applied luminous hour markers.  The hands are painted, partially, in black with a luminous line. The sweeping second hand is not painted.

The slide rule is the name of this type of internal bezel. How does it work?  In a few words it is used for multiplication, division, distance and volume conversions, time calculations and percentages.

The movement is the well known 8200A Citizen calibre. It is an automatic movement (it can be also hand winded) beating at 21600 bph with a quickset day and date. It has a unidirectional winding rotor and 21 jewels. Nothing fancy, just an usual Citizen “workhorse”. It has a power reserve of about 44 hours.

The bracelet is a stainless steel one, with a polished center and brushed sides. It compliments the overall shinny design of the watch nicely. It has folded “H” shaped links and a signed “Citizen” clasp. As usual, very comfortable.

The PAF engraving (and the up pointing arrow) suggest it was in use by the air force and it seams that this was the Pakistan Air Force. So that makes it a tool watch, used for what it was meant to be used.  Just a nice, interesting touch.