Hi David, What are those open heel fins you posted? They look very similar to early Churchills, but not exactly.
You can visit the Finnish Diving Museum web page focusing on fins where the above image is posted if you follow the link to the
Finnish Diving Museum. The caption beneath the picture there reads "Barakuda Original avokantaräpylät, 60-luvun alku", which is Finnish for "Barakuda Original open-heel fins, early 1960s". Hamburg-based Barakuda was the leading diving equipment company in the Federal Republic of Germany and its Original non-adjustable open-heel fins were manufactured from the early 1950s to the late 1960s. Here is a close-up of the markings embossed on the fin:
Germans tend to include a warning message on their products. "Nass oder mit Puder anziehen! Nicht darin laufen!" is German for "Put (these fins) on when they are wet or (dusted with talcum) powder. Do not run when you are wearing them."
The fins were also exported to other countries, including the UK, where I live. Here is a page from the Yorkshire-based Aqua Marine Sports catalogue of 1966:
The use of the term "Admiralty pattern" by the Yorkshire retailer is designed to place the Barakuda Original in the category of a "military-style" fin. During World War II, hundreds of Churchill fins were sent over by ship from the USA to the UK for use by British naval frogmen.
The Special Products division of the Dunlop Rubber Company was tasked back then to fashion more rubber fins based on the American design:
After the War, England's Siebe-Gorman diving equipment company took over the design. This from the SG 1963 catalogue:
Finally, the asymmetrical fixed open-heel design of the Barakuda Original was even adopted in the Soviet Union when it came up with its first post-war fin in the 1950s, named the Model 1 (Модель № 1) :
Interesting that we probably now associate this fin design with bodyboarding rather than underwater swimming, yet wartime frogmen achieved incredible exploits using them!