In reply to:

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"TPSI" was never used in the original data. Pressure was simply expressed as "X tons".

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Huh??????
400, don't go betting your gun collection on that one mate!


Yeah, pressure may well have been sometimes expressed as "Tons" in the "original data" but that was definately referring to "Tons to the Square inch" or "Tons per Square Inch" or "TPSI".
"Tons" was used as an abbreviation.

"X tons" is a measurement of mass or weight, not pressure.