Ha! psi is for juniors....
This gauge is for serious steam: Tsi, Tons per square inch.. 1 Tsi=2240 psi..
(this is an imperial steam gauge, the american ton is only 2000lbs, known here as a short ton, the imperial ton, or long ton, is 2240 lbs, whereas, just to confuse matters, the metric ton, or 'tonne' is 1000kg, or 2205lbs)
So this gauge tops out at... just under 18,000psi (17,920psi)... I think I'd want to be about half a mile away if it approached that in real life.
(The inner dial shows the maximum pressure reached, the glass front opens for resetting.)
I was planning to pipe them all up in thick copper pipe, all over the chimney breast above the fire, and fit a clock mechanism into one of them, never got round to it, of course.