 The black faceplates of the "blackface" era Twin Reverb will say either "Fender Electric Instruments" (FEI) or "Fender Musical Instruments", (FMI) depending on the date of manufacture.Units made before the takeover of Fender by CBS in 1965 will be marked Fender Electric Instruments, and be worth a bit more on the collectors market.The more common speakers found in Fender Twin Reverbs include Jensen C12Ns, Oxford 12T6s, JBL D-120Fs (an upgrade at the factory), Altec Lansing 417-8Cs, Utahs and, in later years, CTS and Eminence models.