I was looking for something else in TPS and ran across a chart that Parker Brothers supposedly used to determine pressure for proofing. It was based on British rules for 1925. It lists definitive proof pressure, service working limits for factory loaded ammunition, etc for gauges 410 thru 10. It dates back to 1934, it is on page 515 in The Parker Story. I will scan it, any one that wants a copy e-mail me.

I learn something every day, and a lot of times it's that what I learned the day before was wrong