I've got several articles in copies of "The American Rifleman" on the history of the US martial and naval Colts. They are full of details on numbers, problems with supply and quality control, anomalies in features, serial numbers, etc. One interesting tidbit:
"These iron strapped Navy-Navy models are also interesting because their guards were not manufactured in Hartford but in Sam Colt's London factory."
Hartford was geared to produce the brass grip frames.
The number of '51 Navy models purchased by the USN were small compared to purchases by the Royal Navy:
"Odd though it may seem at first glance, The British navy bought four times as many Model 1851 Navy revolvers as the US Navy did during the 1850s. Great Britain purchased 9,500 Colt Navy's from Colt's London representatives for the Royal Navy in five lots between Mar. 08 and Aug. 14, 1854, according to R.Q. Sutherland and R.L. Wilson in "The Book of Colt Firearms." Thousands were earmarked specifically for the RN Black Sea and Baltic fleets during the Crimean War.
During the entire period 1852-59, by contrast, the USN bought only 2,650 Colt Navy's. The answer lies, of course, in the fact that Britain was engaged in the Crimean War in 1854 while the US Civil War did not come along until and stimulate Colt sales until 1861."
One of the first USN purchases of "50 plated '51 Navy's plus 25 larger Colts of Army calibre and apparently 25 Model 1849 Colt Pocket Model revolvers in .31 calibre was for Commodore Perry's 1852 'gun boat diplomacy' trip to Japan. The US wanted to make the best possible impression on the Emperor.
If you google 'HMS Warrior', you'll see a restored/preserved British warship with racks of RN Colt Navy's.
The USN also used R-M conversions of their '51-'61 Navy models well into the cartridge era, throughout the entire 'Indian War' period, declining to adopt the '73 SAA after failing the initial Naval Ordnance tests, as was the S&W American despite the fact that USN liked the simultaneous extraction feature.