I've kept a pair of older 2 channel models:
1993 Dual Rectifier Revision F (Blackface)
1994 Dual Rectifier Revision G (Blackface) - "Transitional Model", meaning it has all the trappings of the earlier models (including a factory serial loop) and was actually built into a Revision C/D chassis. It's the most odd transitional model I've ran across, and Iv'e had tons.
I keep both because they're set up a little different, and tonally they're a little different as well. At one point I had 8 of the old 2 channels sitting in my basement (which included one from every revision)!