The problem with CIP is that you have a bunch of countries, many of which have had proofhouses for a very long time, but all have continued to use their own proofmarks.

The British continued to use their own system of measurement for proofmarks (tons, which was actually service pressure rather than proof pressure) and could not be converted to anything anyone could really understand if you multiplied by either regular or long tons). CIP converted to the metric system and started expressing proof pressure in kg or bars (although most CIP countries, with the exception of the UK and Spain, didn't use a proofmark with a numerical value). However, at that time, they were still taking their pressure readings via the old lead/copper crusher method. And even though they converted to electronic transducers, they continued to use the same (crusher value) proofmarks. A bit confusing, to say the least.

As a result of the most recent change in CIP proof rules (2006), there are no longer any numerical proofmarks denoting either proof or service pressure. You have STD (standard), the old 850 bars as measured by crusher but 960 bars as measured by transducer, or SUP (superior) which is the old magnum proof.

Which proofhouse does it better? Well, I am aware of a new Spanish sidelock, from one of that country's top makers, which
suffered a "catastrophic failure" in the form of a burst barrel, doing some damage to the shooter. Again, new gun with new factory ammo appropriate for the gun in question. Seems that gun passed Spanish proof with a wall thickness in the thin spot, where it blew, of well below .020. I own and have owned both Spanish and British doubles, and have no ax to grind one way or the other. But based on that alone, I certainly wouldn't go overboard acting as a cheerleader for the Spanish Proofhouse.