John tracy - It's the KT120 tube, although it was recently discussed being used in the Dynaco ST120 amp. See below:
http://db.audioasylum.com/cgi/m.mpl?forum=tubes&n=229772&highlight=kt120&r=
http://db.audioasylum.com/cgi/m.mpl?forum=tubes&n=229772&highlight=kt120&r=