Thanks to Jim Martin for providing this information

14 Feb 1917
44 Win. for Model 73' - Service Pressure 13,000 (cup), Proof Pressure 16,500 (cup)
44 W.H.V. for Model 92' - Service Pressure 18,000 (cup), Proof Pressure 23,500 (cup)

By the 1930's the 44 W.H.V. was reported to be 22,000 (cup)