Before revision: Nonetheless, for its efficiency and low cost, the blueprint process, further simplified and mechanized by the turn of the 20th century, became the most widely used reprographic process between the mid-19th century and 1940s .
After revision: Nonetheless, for its efficiency and low cost, the blueprint process, further simplified and mechanized by the turn of the 20th century, became the most widely used reprographic process from the mid-19th century through the first half of the 20th century .