Dutch second impression paperbacks

Not sure if this fits better in the Recent Acquisitions thread, but these came in this week: first impressions (1965) of the Dutch Prisma series pockets with covers by Cor Blok, stated “second impression, revised by the translator”. Very happy as they seem to be unread. These first impressions are noticeably thinner than my later 1974 impressions.
Confusingly, these pockets share their impression number with the one-volume hardback published in the same year, which Beren explains in detail on his website.