Those coaches sound impressive. I have some older ball bearing wheelsets, and they add some weight to the cars.
I do see some children in the sheet metal picture, but they seem a little older than the painters. I started working retail at 16 years old, but I was pushing a lawn mower for cash way before that. The working conditions of the Marklin factory appear to be a little nicer than what I have read about the 19th century English factories.
George
