Brand: Gruen

Model: Precision Day-Nite "Jump" Dial ref. 510 Rss CA (RARE); Swiss Made circa 1960s

Case: Rare solid stainless steel case with screw-down back is approximately 34mm excluding the original unsigned winding crown

Strap: 18mm handmade textured taupe calfskin strap with contrast stitching and polished stainless steel tang buckle

Movement: Gruen cal. N510CA manual-winding movement (17 jewels) with original dust cover; specially modified for day and night "jumping" function; 18,000 BPH; Swiss Made

Features: Stunning original silver sunburst dial with open aperture hour markers to accommodate the unique day and night "jumping" feature; a colored disc flips underneath the dial from black during daytime hours (6 AM - 6 PM) to fluorescent "nite-glo" green during nighttime hours (6 PM - 6 AM); original black luminous hands; original black center sweeping-seconds hand; incredibly rare model with solid stainless steel case; domed acrylic crystal

Condition: Fantastic original condition overall with only minor honest signs of wear consistent with age and light use; solid stainless steel case exhibits nice bevels on each of the lugs; crisp screw-down caseback remains clearly legible with the original brushed finish in tact and a few minor toolmarks; beautiful original silver sunburst dial; excellent original black handset with all luminous material in tact and matching

Other: Looking for a unique conversation piece? Look no further than this innovative Gruen Day-Nite available for sale from Justin's personal collection. Gruen was way ahead of the times when they released this complication way back in the 1960s and it still doesn't get much more interesting than this today. All Day-Nite models are exceedingly rare, but try finding one with a solid stainless steel case in this condition... For those that are not familiar with its functionality, the dial features open aperture hour markers with a colored rotating disc underneath that displays black during daytime hours (6 AM - 6 PM) and fluorescent "nite-glo" green during nighttime hours (6 PM - 6 AM). The 34mm steel case wears comfortably on the wrist and slides nicely under the cuff of a dress shirt, but it can also be worn casually with a t-shirt and jeans. The mint green hour markers are next-level cool!