Signedplate on top: TYPE 400 / POWER AMPLIFIER AND PLATE SUPPLY / 110 V.A.C. 60 CYCLES SERIAL NO. 966 (GR logo) USING UX-213 RECTIFIER AND UX 171 AMPLIFIER TUBES / MADE BY / GENERAL RADIO CO. / CAMBRIDGE, MASS., U.S.A.
Inscribedpainted on side: [open triangle mark]