The use of cast iron in many Spanish guns led, interestingly, to a total and complete misunderstanding of the term "pot metal". In every French and Spanish home a place of honor on the stove was given to the cookpot, into which went about everything in the kitchen except the cat. Most of the family's meals came from that cookpot ("marmite" in French, "marmita" in Spanish). Since no great strength was required, those pots were made of cheap cast iron, commonly called "pot metal".
Much later, Americans who never saw an iron cookpot, read or heard the term and were puzzled by it. Some young gun collectors, believing that quality guns had always been made of steel, but being familiar with the various zinc alloys used in cheap guns, concluded that "pot metal" meant metal with a low melting point that was melted in a pot, rather than the material a pot was made of. That misunderstanding has now become so ingrained into the gun language that it even is repeated in Wikipedia, which is often cited as the source of all wisdom by the naive.