Gruen Jumphour Day/Night

Here is a very cool vintage Gruen precision Jumphour. 

The fun complication of this watch is that each hour marker is an aperture for the wheel below it. From 6pm to 6am, the wheel features a luminous green radium (the illumination is no longer). From 6am to 6pm, the wheel switches to black. 

The radium on the dial has patina'd the white dial, and it looks striking. The day/night wheel is in great condition with no apparent damage or wear, despite the lume no longer luming. 

This watch features a high dome crystal, and measures about 34mm without the crown. The manual wind Gruen 511 movement has been fully serviced with a new mainspring and keeps great time.