500 Grains is correct. It's a nice story but it's fantasy. Bench time to build a "Royal" or "Modele Deluxe" double rifle was 1200 to 1400 hours or more in those days. This rifle was substantially complete when the order came in. There were quite a few substantially complete projects laying around in the British trade in 1921 - orders placed in 1914 - 1915 by gentlemen killed in WWI (750,000 British were killed in action). Keep in mind that not all of Holland's best double rifles were built by Holland.

This story is akin to that of the pair of Churchill "bests" ordered by the Prince of Wales in 1931. They were delivered in something like 2 or 3 weeks. They were needed quickly as HRH was departing on a trip to South America. By that time, Churchill was having most of it's guns built for them by a variety of makers in Birmingham. Those guns were sitting in a rack in Birmingham, complete except for final stock dimensions.
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