A couple of observations about ASI styles (reference post #31):
The 'steam boiler' style gauge can give a quick estimate of speed based on position around the dial. Whatever you are used to, (automotive with zero on the left or aircraft with zero at 12 or 1 o'clock) a quick glance at the pointer position gives you an idea where you are at. Speed tapes(bottom) and odometer style mach readouts (middle) require reading and interpreting a numeric value.
One question: In the top figure (2.7.1), how do you interpret Mach number? I assume the Mach dial rotates to compensate for OAT and places the current Mach next to the corresponding IAS. The single pointer would then indicate both Knots IAS and Mach. Correct?