Colt registered and seems to have begin production of his 1849 and 1851 pistols in his London factory in 1853.
Up to around s/n 3000 the trigger guard and backstrap was silver plated brass. From s/n 3000 thru 37500 the London made guns had a iron trigger guard and backstrap which the British preferred.
The London factory seems to have stopped making the pistols in 1856 having produced around 37500 guns.
London Colts following the closure of the London factory were made in Hartford. These are known as the "Hartford-London" Colts.
The author of the book, "COLONEL COLT LONDON", (Joseph G. Rosa) where most of this information came from designates these as the "Fourth Model" and says on page 169,
"This version is distinguishable because of the large rounded triggerguard. Most triggerguards were manufactured in brass but some iron guards and straps, which perhaps owe their origin to the London factory are to be found. Some late production fourth-model Hartfords were numbered in the London serial range. It was the fourth model that was cut for shoulder stock..."
