Comparison: 1971 Vs 1973 Vs 1976 Marshall Super Lead model 1959, ALL KNOBS ON FULL. Epiphone Les Paul Special II Ltd with a Burstbucker II in the bridge. Cab 1971 Marshall 1960B with 1973 G12M25 75Hz T1221 Pulsonic Celestion Greenbacks. Close mic Sennheiser MD421 U5, room mic AKG C414BXLII omni at 10 feet. Sound interface Apogee Duet into an IPad with Cubasis, recorded dry with no post processing. The main difference between these amps is probably down to component drift or possible mods. To be able to play a 100 Watter into a single cab I backed it off 8dB with a Hotplate (no EQ compensation active)