Kennett's article on Italian proof runs pretty much along the same lines. Their standard proof of 12,800 psi and the Belgian proof of 12,900 psi are certainly close enough to be considered identical. Likewise the higher proof pressure for smaller gauges.
CIP member countries may have adhered to the same basic standards, even if sometimes they added optional proofs (like the Italian "reinforced proof", which dates from 1962). And continue to use very different proofmarks. The Brits really confused things when they went to the "tons" proofmarks in the 50's.
I'm still wondering whether they all transitioned to transducers at the same time. There are some clues from countries like Spain, which includes the proof pressure as a proofmark. But the ones that don't do that, like Belgium and Italy--or for the ones like England that used crusher values as proofmarks until 2006--leave the situation less than clear.
