Complex sentence: Early toy books were hand-coloured in print-shops, often by children apprentices although by the mid- 19th century mechanical colour printing became more prevalent, and toward the end of the century children's books became quite elaborate.
Split into simpler sentences: Early toy books were hand-coloured, often by children in print shops. By the mid- 19th century colour printing became more prevalent, and toward the end of the century some of the books became quite elaborate.