Hello John and All
England - some Moulders worked at a Foundry where metal is cast into shaped moulds.
My British Dictionary and Thesaurus (pub. Glasgow) seems to agree and in the U.S. spelt Molder without the letter u.
Someone who forms or shapes metal, by using a mould.
Mould - 1. cast, die, form, matrix, pattern, shape.
4. carve, cast, construct, create, forge, fashion, form, make, model, sculpt, shape, stamp, work.
Mark