Can't be 300: 4/6L6s, not 300's power. 1/Was there a pre-'91, single-12", 22.5" combo w/Presence & Limiter on front? I can't find one. 2/A Simul-Class frame w/an SOB plate is so wrong. Is there an SOB orphan out there w/no serial#, or is this a Simul-Class frame that -never was- Simul-Class...