For the most part, everything was wrought iron, case hardened often, except the steel springs and the steel face of the frizzen.
"Wrought Iron" is nearly pure iron, simiar to today's 1008 steel, from which "black iron wire", a hardware store item, used to be made. The difference is that there is a considerable amount of slag in wrought iron, essentially strings of calcium silicate glassey stuff mixed with iron oxide. It is the slag which makes wrought iron (relatively) easy to forge weld.
But it is soft, so to get one's tumbler, sear, bridle, lockplate hard enough for use, that 18th century hardware was "casehardened" Packed in charcoal, maybe wood, maybe bone, maybe charred leather, likely some mix of two or more of these. Heated a nice red for at least an hour, then dumped into a pot of water.
Late 18th and early 19th century English and maybe American locks may have used "cast steel" for internal parts. Cast steel of the time did not mean it was a casting, it simply translates to something more or less like modern plain carbon steel, maybe 1060 or 1095.
"Steel" in 18th century England meant a couple of different things. The most common was made by case-hardening wrought iron skelps in a large pack for about a day at bright red heat, say 1750F give or take quite a bit. Eventually the bar got carbon soaked most all the way through and became "blister steel", still full of the slag it had as wrought iron. Various grades of steel were made by shearing these skelps to shorter lengths, bundling them together and forging the bundle into one piece, to give it somewhat more uniform carbon. That was "shear steel". This, and the cruder blister steel, were used well into the 19th century.
About 1740 in Sheffield, England Mr. Huntsman learned how to put several pieces of blister steel into a curcible, and using techniqes learnt from his pottery friends, actually melt it. Poured into an ingot, the slag floated to the top and he got an ingot of more or less uniform high carbon steel. Being able to actually melt and cast steel was a new thing to the English (the Indians had been doing it for well over a thousand years by then) so this "cast steel" was all the rage. Made good tools and springs. Later on a "decarbonized cast steel" was made, low enough in carbon that it could be used for pistol barrels. Allen & Thurber pepperboxes were an early example, all being marked "CAST STEEL" Sam Colt bought his cast steel from Firth, for revolver barrels and cylinders.
The Germans had some different process for making good steel, but unfortunately I am not familiar with it.
Glad I could help confuse you.
