Thus, I suppose, that these “Irish” Caravelles never carried any Irish registrations, painted on them. In my opinion, these registrations were rather the “paper” registrations, for ferry flights from Spain to Taiwan only (or, maybe, those registrations were the call signs only).

No, as I said above, there is a picture of EI-AVY (marked as such – basic Iberia colours, no titles or logos but with the Irish registration) in John Wegg’s Caravelle book. The caption says that it is landing in Rome on its delivery flight from Spain to Taiwan. The registrations were undoubtedly painted on the aircraft, but I suspect for only a short period.

Andy