1960s Vintage Gruen Airflight Jump 24 Hour watch, ref 510rss 24 hour pilot watch.
The watch is keeping time to within +8 seconds a day, with a high amplitude and low beat error.
 
This is a rare and very collectable Gruen watch known as the Airflight. The dial configuration is very adventurous in that it is a cleverly designed 24-hour dial system. At first, you see the typical numerals of one to 12, but as the time passes noon, the entire set of numbers jumps over to reflect the hours from 13 to 24; it goes back to one to 12 again at midnight. Gruen carved out a Niche for adventurous pilot watches with other examples including the Gruen Pan-Am.
The watch has it's original dial which hasn't been refinished. The only non original aspect is the crown.
 
Please see the images as these compliment and aid the description provided below.
 
Dial: 
The dial is original, unlike many that have been re-finished. There is a small circle of wear near the canon pinion, likely due to hands rubbing in the past, as well as a slightly lighter ring which has removed some of the Gruen signing. Please study the images. These marks do not detract from the overall beauty.
 
Hands: 
The hands are original and have some signs of marking. Overall they aren't bent and are in good condition.
 
Glass:
The crystal is in very good condition with no scratches.
 
Crown: 
The crown appears to be a later replacement. In good condition.
 
Case: 
The case is gold plated and in average condition with no dents or deep scratching, only light surface scratches. There is wear to the gold plating, on the tips of the lugs and the sides.
 
Caseback: 
The Stainless Steel case back is in good condition. It has light surface scratching and one slightly deeper mark where a tool clearly slipped.
 
Strap:
A new 16mm genuine leather strap.
 
Movement:
A Gruen N510SS movement, with 17 jewels and a power reserve of 42 hours. Keeping time to +8 seconds a day with an amplitude of 250 and a beat error of 0.1 m/s.
 
Case dimensions
Case width: 35mm
Case width with crown: 38mm
Case length: 35mm
Lug to lug measurement: 41mm
Case depth: 10.5mm
Lug width: 17mm