The mask under review by the OP has compensator bosses for squeezing the nostrils, enabling ear clearing:
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These finger wells go back to the late 1950s French patents of Georges Beuchat and Roland Forjot, who produced masks commercially incorporating the feature for their diving equipment companies Beuchat and Marin. They were widely copied and adapted by manufacturers in many countries around the world, including the USA and the Soviet Union. It was harder to clear the ears when using oval masks without these compensator bosses, but not impossible. Divers would press the bottom of the mask skirt against the nostrils to close them then exhale nasally.
The nose pocket design used in modern masks is actually quite an old idea that originated in the Cressi Pinocchio mask from the early 1950s:
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Pictured above is the inventor, Luigi Ferraro, wearing his invention, the Cressi Pinocchio mask, which was devised in 1952 and is still in production.