Thanks for the great step by step post! I have the same bracelet myself in 22mm and the clasp type is called a butterfly. It is usually found on dress leather straps or bracelets. If I can get a Tuna this year, I will try this bracelet on it. And yeah I hear you, the absence of a diver's extension on aftermarket bracelets has also driven me a bit insane, up to the point of asking around if any local watchmakers can create a custom extension for the Super Engineer. Sadly the answer is no so maybe I will have to go your route.
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