Further complicating for me the Verithin history is recently acquired earliest serial number, but best ever grade Extra Precision. Original in cheapest gold fill Gruen U.S. factory round case. About 18 years before pentagon case available. Well used, but functional. I have not seen another for sale. It is the most accurate model preceding the similar near 20 year later Gruen 50th. The really rare, and cosmetically similar to 50th, Madretsch gold plated Verithin has serial 140000 compared to this one 138000. First of the Verithins were 1904. These 2 movements are near that date although the fancy one is originally in the best Gruen 18k case marked 1926. Visible in 2nd click on mvnt. photo is no screw in winder clutch, Madretsch style regulator, mustache lever (pallett fork). I believe the 2 old ones represent the first of the famous Verithins and that Leo Alby's small Madretsch factory made the first ones and some specials like the one here. The 21j Extra Precision represents earliest production at the new Swiss factory. The only sure thing is that the marking DG&s ended 1910.