This MRO or Mine Recovery Outfit Helmet was built by C.E. Heinke & Co. Ltd. for Siebe Gorman under commission from the Royal Navy during WWII for the purpose of recovering and deactivating German mines.
Rather than being bolted to the top of the dive suit, the corselet of this helmet was glued under the top of the jacket. Unlike regular dive suits which were all one piece, the MRO dive suit consisted of separate pants and jacket, each with rubber at the waist to seal it. When the diver put on the jacket the helmet was already attached. The helmet is considered shallow water with a maximum depth of 120 feet, though they were most often used in coastal waters at lesser depths.
It was key for the mine recovery divers to create the smallest disturbance possible under the water. Mines were often sound reactive, so much so that bubbles from a regular dive helmet were too loud for safety. The rear connections on the helmet were hooked up to a self contained rebreather unit with a CO2 scrubber and connections for their air tanks filled with a nitrogen/oxygen mixture optimized to reduce decompression time. There is a side exhaust but the holes are small so that any escaping air makes only small, quiet bubbles. Additionally the helmet and all other metal pieces of the MRO diving dress were made from nonmagnetic metals as magnetic metals were also known to set off mines.
This helmet has been polished but was obviously used. The photos shown are for reference to show the full gear with the rebreather attached. The photo also shows the interesting front light, hinged underneath so it was never separated from the helmet.
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