Despite its name, white wasnt the only color produced: opaque black, pink, and green were some of the more expensive variants of milk glass. Generally, pieces dating from the mid-19th through the early-20th century are considered the most valuable.

How do I know if my glass paperweight is valuable?

Color: The color, clarity, and brilliance of the glass are extremely important when judging the quality of a paperweight. A yellowish cast to the glass is characteristic of Chinese weights made during the 1930s and 1940s. The glass in some classic period Bohemian weights is slightly yellow in color as well.