In 1939 Fenton Art Glass first introduced their hobnail glass and in those early years it was in translucent colors. Milk glass hobnail was introduced by Fenton in 1950, and proved to be one of their most successful products. It kept the company going during the very difficult years when many other glassworks closed down. Just about every Fenton shape has been produced in hobnail milk glass. Pre-1958 Fenton milk glass is said to be easily distinguishable because it is less dense, less opaque, than their milk glass made from 1958 onwards. Also, the Fenton logo was introduced on milk glass from 1974 onwards, with a tiny number 8 below the word Fenton for pieces made during the 1980's and a tiny 9 for pieces from the nineties.
I am curating several pieces of Hobnail glass in my Etsy store:
Click on link to see listing