Not sure, but I think those might be 1960s instead. I see "Made in Holland" and Schick had production in the Netherlands as early as 1963. The Krona badge was in use that early too. Schick originally used the Krona brand in the late 1950s and early 1960s for carbon steel blades, both injector and DE. Then around 1963 they followed Wilkinson-Sword into the new market for PTFE-coated stainless blades, which became known as "Super" or "Extra" blades. By the late 1960s to early 1970s Schick was shifting use of the Krona badge toward the new Krona-Chrome blade, with a chromium coating in between the steel substrate and the PTFE coating. Still later the Krona brand went away completely, in favor of Schick Platinum Plus and similar branding. In general by the 1970s Super blades were shifting toward larger packs of 10 or 15, because they were no longer the flagship blades.
Another reason to think they might be fairly early is that there are not patent marks visible. Later packs with Krona Super blades often mentioned a Schick patent on an improved coating process: US3203829 published in 1965. Schick held corresponding patents in the UK, Germany, and Denmark, although the publication dates varied.
