My apologies to anyone who mistook my post for an attempt to lecture on this complex subject. It was meant as a flippant and amusing comment but one that had an underlying truth, offshore CAT in the 1970's was anything but 'kosher'. I have to tell you that in some parts of the world it's still like that.
What of PC2e & E - Back in the days when these concepts were in their infancy (the 1990's) the dialogue we used in correspondence was a shorthand that made reference to the offshore requirements in so-called 'hostile environments' (e.g. The North Sea) - this was PC2 but this version of PC2 was only accepted by the regulator (then the UK CAA) on the basis of an acceptable exposure time. (This was calculated by experts using probability theory I believe). Hence PC2e
The version of PC2 embraced by JAROPS 3 NPA38 (around 2004 I recall) and was intended to make up for the fact that JAR had recognised that their goal of universal PC1 was unattainable in the offshore environment and a better version of 'exposure' was required. The version required a statement of engine reliability (less than one failure in every 100,000 flight hours) by the airframe manufacturer, bolstered by HUMS or something equivalent. To differentiate we use the acronym PC2E.
The advent of EASA meant that things may have taken a different path but I haven't been following that subject area very closely as offshore (Europe) is not my main focus.
G
PS - If we are to compare CAT with Mil Ops then I think it's fair to comment that when you have to manipulate data and create algorithms and invent new performance/operating categories to allow folk to go about their daily tasks offshore then we can comment that the regulators are being creative. If it is something less than absolute PC1 then Joe Public is entitled to call those ops 'quasi military' - i.e. they adopt a regime appropriate to the essential nature of the task whilst maximising safety.