The P53s were a major design change for the British Military.
The first Pattern to use barrel bands {earlier barrels were pinned to the stock}. Bore size was reduced to .577". Rifling was changed, barrels were shortened, etc.etc.
The P53 type I used screw clamping bands and other changes such as the rear sight, 39" barrel 3 L&G with one turn in 78" {slow twist}.
This type was made from 1854-1855
The Type II used from 1855-1858 used solid barrel bands secured by band springs into the wood ahead of the band. It used a "swelled" ramrod head, rather than a spring device in the belly of the stock. There was a bit of variations in the parts and rifling in the later Type IIs. as the Pattern 53 was still being perfected.
The Type III, which most collectors are familiar with, was produced from 1858 and 1863 noted with a thick jag-head ramrod and screw clamping bands. Contractors continued to produce them after that date but the locks were not dated. The rod was now retained by a spoon-spring in the stock. Sights went from 900 to 1000 yards. The caliber remained at .577 but the 3 groove rifling now used progressive depth from breech to muzzle. Some London Armory rifles and P53s were purchased by the CSA.
A IV model was also made but only at the Royal Enfield Arsenal and at The London Armory. These machine made guns had interchangeable parts. All of the prior types made by contractors had hand-fitted parts.
Some type 1 and 2's were shipped to the CSA, but were most likely case fillers, purchased by civilian purchasing agents, and none were contracted as far as is known.