Two crowns, one of them for arithmetic.

Most slide-rule watches put the scale on a bezel you turn with your fingers. The Nighthawk puts it on an inner ring and turns that ring with a second crown at eight o’clock, so the outer case stays fixed and the scale cannot be knocked out of alignment in a sleeve.

The scale itself is the same circular slide rule pilots used before calculators: line up two numbers and it multiplies, divides and converts. The crown at three sets the time and the date in the usual way.

The dial looks like a chronograph and is not one. The single register near ten o’clock is a 24-hour display for a second time zone, which is more use to a traveller than a stopwatch, and there are no pushers on the case. Oversized numerals at twelve and six, the twelve outlined in red, orient the dial at a glance.

Calibre B877 is Eco-Drive: charged by light, rated by Citizen for six months of running on a full charge, and never opened for a battery. A screw-down caseback and a 200m rating make it a Promaster in more than name.

The BJ7000-52E is 42mm across, 13mm thick and 47mm lug to lug according to izreview.com, on a steel bracelet with 22mm lugs. Those are ordinary pilot-watch proportions, larger than the 40mm Navihawk but well short of Citizen’s biggest aviation pieces.

The crystal is mineral glass with a non-reflective coating rather than sapphire, which is the one place the price shows. Owners have been buying this reference for two decades regardless, which says something about the rest of it.