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.
This constant speed propeller was unique because the hydraulic pump, governor and related pitch change mechanism were contained within the propeller hub assembly.
This object is not on display at the National Air and Space Museum. It is either on loan or in storage.