Gauges were not require to be stamped on UK barrels until 1855. However, a few makers always did it among them was Reilly. It is a simple straight-forward number - no diamond. I'll post Diggory's excellent chart again:
![[Linked Image from i.imgur.com]](https://i.imgur.com/5HGiUvX.png)
The under-lever was patented by Jones on 7 September 1859, patent 2020-59. The patent becomes public property in 1862 - how or why the patent was broken is unknown to me but surely there is literature about it. (Jones surely got the idea from the French gunmaker Berringer).
Pin-fires continued to predominate up to around 1872 per an unscientific measurement based only on my Reilly database and some of the ones I've labeled "converted to center-fire" might have been original centerfire. See the line I posted where a realization dawned that there were were two basic designs for central fire from 1865 on. 1866 really was the dawn of the shotgun center-break central fire gun when Boxer and Berdan almost simultaneously invented a primer that could be used in a C-F shotgun shell.
Stanton took out his patent 367-67 on 09 February 1867 for rebounding hammers and an improved version on 30 Dec 1869 patent 3774-69. However, it wasn't used widely until much later and you can find guns being made into the 1880's with non-rebounding hammers.
