@croydon - Well, even blacksmiths sometimes "cheated" and simply bought pre-made ingots of metal. I was in a museum the other day and they had some old samples of the different kinds of metals that were available in market places 500 years ago.
They sold massive chunks of lots of different kinds of metal like copper, iron, lead and so forth.
Actually there are probably special kinds of metallurgist experts who help with researching those kinds of historical artifacts.
I imagine they have quite a lot of work at archaeological sites, testing the age and purity of metal and investigating the uses of different objects.
It must be quite fascinating, being able to build up a story based on a single object and maybe trace where the metal came from, how it was formed and what happened to the object after that.