[rotorwrench]

The only way to affect a specific hardness on the old cast iron formula was to carefully control what was added in the mix at the foundry. If you look at the note. It mentions taking a reading on a scrap block since the Brinell test leaves a larger mark than Rockwell. Casting technology is a lot different now than it was back then. They were trying to insure uniformity in the casting process. Ductile or "nodular" cast iron had not been developed yet.