Masterlure plugs were used by fishermen in the late 1940’s and early 50’s, and were made in Brooklyn, New York, USA, by W J Schoeninger Company and Masterlure Inc. During this timeframe the lures had large, glass eyes and were stamped on the belly in script. Sometime in 1953 the company moved to Staten Island, NY, and was probably sold.
In 1955 the company was sold again and was taken over by the Seneca Tackle Company in Rhode Island. Masterlure by Seneca was manufactured into the 1960’s.
You can read up on Masterlure and see more pictures at this site: