I’m checking out my 1989 Dual Showman right now to update these specs — it’s the model with no reverb. The dimensions of the head are 27.5" wide, 9.5" high, and 11" deep; I just measured mine, so I’m certain of that. The tube complement includes three 12AX7A (7025) tubes in the front row, followed by one 12AX7A, one 12AT7, and four 6L6GCs in the back row. Mine still has all the original tubes except for the power tubes, which are a matched set of Mesa Boogie 5881-6L6s. The corners and handle hardware appear to be black powder-coated aluminum. The front mid knob also doubles as a pull-out mid-cut switch (a “scoop”), and combined with the treble boost and some chorus or delay, it gives one of my favorite clean tones ever. The front panel layout is as follows: Volume, Treble (pull for boost), Mid (pull for cut), Bass, Channel One/Foostwitch inputs ×2, Channel Two/Parallel channel mode inputs ×2, Gain, Treble (pull boost), Mid (pull boost), Bass (pull boost), Presence (pull notch), Volume (pull channel select), Damping (Hi/Med/Lo), Output (Lo/Hi), Standby, Power, and a small red pilot lamp. On the back panel: Fuse (4A-125V Slo-Blo), Preamp Out, Power Amp In, Power Amp Thru, Loop Level selector (-16dBv, -7dBv, +4dBv), Output Bias Adjust, Output Balance Adjust, Footswitch jack, Balanced Line Out, External Series Out, Main Speaker Out, External Parallel Out, and an Impedance Selector (4/8/16 ohms). I noticed a few discrepancies compared to other references, so it’s probably worth looking into further.