The American Defense Service Medal was issued to members of the United States Armed Forces who served between 1939 and 7 December 1941. All the information came from the book Military Medals of America at https://www.amazon.com/Military-Medals-America-Frank-Foster/dp/188445271X/ref=pd. The medal comes in several formats and has four different service bars making it an unusual medal to find with a service bar as it is the last American medal to use service bars as was done in world War One.