re: barrel steel. Crown steel was introduced for the Pigeon Grade in 1893, A1 in 1894, the No. 3 about 1895, and in 1898 the No. 2.
Nitro steel was introduced in 1898 for the No. 3 and Pigeon and later the No. 4 and No. 5.
Armor steel appeared in 1898 with the 00, and Royal steel for the F grade hammer gun in 1898. London steel was used for the No. 0 and Special steel for the No. 1 starting in 1907
https://docs.google.com/document/pub?id=17ixogftgITEblNUWtmFBv96ZvgjK6eFell8GsAWd-KI I have done composition analysis and tensile testing on Armor steel barrels but for some reason no one seems to want to chop up a Nitro or Crown steel barrel for me
Scroll down about 1/2 way here
https://docs.google.com/document/d/1dnRLZgcuHfx7uFOHvHCUGnGFiLiset-DTTEK8OtPYVA/edit 
