U.S. Army Air Forces Sight, Gun Type N-9
PART NUMBER:N-9 (Spec. No. 24890)
MFG: Spertl Inc.
AIRCRAFT: P-51D, P-63, and A-26 Invader.
CONDITION: As Removed
DETAILS: Good condition and hard to find! Used on the P-51D, P-63, and A-26 Invader. 

Technical Drawing Available at AirCorps Library: http://www.aircorpslibrary.com/Drawing/Viewer/106-61013/