Piece of the original ingot of R.F. Mushet's self-hardening steel

Robert Mushet was an English metallurgist who invented "R Mushet's Special" steel in 1868. This was a self-hardening tungsten alloy steel which was the forerunner of a whole family of tool steels, the most common one being high speed steel which contains 18% tungsten, 4% chromium and 1% vanadium.This steel has the property of "red hardness", that is, it still retains its hardness even when cutting at speeds which make it glow red hot.