While surfing online recently I chanced upon a couple of artefacts from the 1950s appearing to show that the phrase "vintage double-hose" might be applied to a snorkel-mask as well as a scuba regulator.
1. Nemrod Haiti. PS/2069.
I am grateful for the above images to the excellent Nemrod Museum at https://www.facebook.com/nemrodmuseum/?rc=p and more particularly for the speed and expertise of response to enquiries about the history of Nemrod diving equipment. I am equally grateful to the Musée Dumas at http://museedumas.fr/, whose collection of "livres & documents" includes the following advertisement from a 1954 issue of France's Skin Diver equivalent L'Aventure Sous-Marine:
2. United Service Agency Super Aquascope.
So Nemrod's "Haiti" "double-hose" snorkel-mask was not unique. The Super Aquascope" wholesaled by the United Service Agency of Nice on the French Riviera bore a close, though not exact, resemblance to the Spanish "Haiti". I wonder whether any other diving equipment companies of the 1950s contemplated adding a similar snorkel-mask to their product range.
The Nemrod company, founded by the Vilarrubis brothers in 1935, is probably already well enough known on both sides of the Pond for me to expand on its history. If not, I refer you to the Nemrod Museum for further enlightenment. The United Service Agency is likely to be an unknown quantity to many of us, however. Despite its name, the United Service Agency was a company headquartered in the French Mediterranean city of Nice. It was founded by American underwater swimming equipment inventor Charles Henry Wilen and Russian expatriate Alexandre Kramarenko. Wilen is known for the patents he took out in the early 1940s, e.g.
"Alec" Kramarenko is mentioned in Guy Gilpatric's famous book The Compleat Goggler, where he is credited with the invention of a "fish gun". Their company, the United Service Agency, marketed "Palmes américaines" fins, "L'Américain" masks and "Fusils américains" spearguns, emphasising the American heritage of company partner Charles H. Wilen.