Details
New old stock ruggedized 9 pin miniature twin triode. Various brands. The 12AT7WA is the Army version, and was commercialized as the 6201. The 12AT7WB is the Navy version. The 12AT7WC is the Air Force version. The main difference between them are the specifications for the centerline and acceptable range of plate current, something that normally does not matter to non-military users.
NSN/FSN = 5960000381656, 5960001794446, 5960007019504, 5960008665467, 5960008803996, 5960009967093, 5960012034334