re: #188 engineer dog

iron requires a much higher melting temperature than copper or tin, so the switch to iron/steel required an advance in smelting technology

They didn’t actually smelt iron/steel until the 1800s AFAIK. Before that it was heated up to make it softer and then just hit with a hammer until it was in the shape of what was needed. There was no way a wood or coal fire could get hot enough to melt it.