Nice chart, Again 10 to the -6 is about what is needed to process a CRT, and simply put you can't get there with a simple mechanical pump such as those used to pump refrigeration systems. Most CRT processing stations use a diffusion pump, sometimes with a Ln2 cold trap.
Now the mechanical gauge on such a system *may indicate* a "perfect vacuum", but really it is not capable of making a precise measurement. It would sort of like trying to measure the speed of light with a stopwatch! A decent ion gauge is needed to measure high vacuum, *not* a barometer type mechanical gauge.
jr
Ion Gauge :
http://en.wikipedia.org/wiki/Hot-fil...nization_gauge
Diffusion pump:
http://en.wikipedia.org/wiki/Diffusion_pump