This Gruen has a cool feature where the hour markers change colour twice a day.


Gruen watches were made in the USA from 1894 to 1958, and after this date the watches were made in Switzerland. By 1977 they were out of business altogether, so our Swiss watch dates between 1958 and 1977. From the styling and movement production dates we have estimated this was made circa 1966.


The N510CA calibre, 17 jewel manual wind movement is still protected by the original dust cover. This otherwise conventional movement has a party piece complication though, and twice a day the hour markers change colour. These were set at the factory to Noon and Midnight, but on this watch it is set to 6AM and 6PM. We can set it back to factory settings if preferred. Gruen released a watch in the 1950’s with a similar feature, but on that watch the numbers changed from say 3 to 15 to represent a 24 hour clock. The feature on this watch is fiendishly simple – a watch works on a twelve hour cycle, and once every cycle a wheel is moved under the dial. It is very similar to a date mechanism, but with twelve apertures at the hour markers and working every 12 hours rather than every 24. The tonneau shaped case is all stainless steel, and does have some marks. The dial is good, and the hands original, but the second hand has lost its lume. This is easy to replace, but it wouldn’t match the hour and minute hands so often looks better missing than replaced. We have taken photos with both the black and green hour markers, and stitched two together so show them side by side. The leather strap is new, and could be swapped for a different colour if preferred. We have taken some photos on a lightly used NATO style strap, just because the colours match so well and it shows a different look. We have also replaced the acrylic crystal.

This watch will be supplied with our branded presentation box and our Certificate of Authenticity.

Please see the HD video for more detail. All photos and videos are part of the description and are of the actual watch unless mentioned. We do not photoshop any pictures, and the images are copyright of and should not be used without permission.


Width with crown 37.4 mm

Width without crown 36.1 mm

Between lugs 20 mm

Lug to lug length 42.7 mm

Case Thickness 9.6 mm

All sizes are approximate.

Included with this watch is a 3 month guarantee and free delivery to UK addresses. If you live outside the UK we can still deliver to most countries. Please see our Worldwide Shipping information, or Contact Us. Payment can be made by most credit or debit cards, bank transfer or PayPal.

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