The Engineering Projects, Inc. was bought by General Motors in 1940 and renamed the Aeroproducts Division. It manufactured many thousands of propellers during World War II, and became a Division of Allison in 1952, which sold the propeller business to Hamilton-Standard in 1990.
The artifact is representative of the first dual rotation (i.e. contra-rotating) propeller to be installed on a production airplane, the General Motors Fisher P-75A Eagle. Only a few of those aircraft were built, with production terminated in 1944 because the original objective was well met by the operational P-38 and P-51. The object is one of two stages of the contra-rotating propeller; the other stage being Object No. A19490055002.
This constant speed propeller was unique because the hydraulic pump, governor and related pitch change mechanism were contained within the propeller hub assembly.