The Heinke MRO was developed for recovery of mines (especially magnetic mines) to a depth of about 55m (180ft). The outfit is a self-contained, semi-closed system that uses a mixed gas supply of nitrox. The system was successfully trialled for the Royal Navy and was to replace the older Siebe Gorman MRS diving apparatus. In 1961, C.E. Heinke merged with Siebe Gorman, but the MROs were never produced in commercial numbers, as new technologies and diving equipment soon superseded it.

Originally, it was thought that about 18 MRO sets were produced in 1958, and then put into war storage. However, one or two additional MRO helmets have been discovered with exhaust and communication modifications.

The Heinke MRO set was supplied with two wooden chests, one containing the gas storage cylinders and the other with associated spares. The spares box is labelled: CANISTER AND SPARES FOR M.R.O. TRIAL ORDER PATT NO.

The MRO helmet shown in the photograph is a prototype helmet from which the final MRO design was developed. The helmet is carefully hand crafted and assembled together from 7 sectional pieces. Window glasses are constructed using two layers of laminated glass that are held in place by rubber seals. The design of this prototype helmet is likely to have evolved from the Heinke 3 bolt, 4 light helmet, as several common design features are shared with it. Similar features include the hinged front faceplate, upper window grill, and corselet/helmet attachments. The final MRO batch production helmet does have a slightly different upper window grill compared to the prototype, but the unusual exhaust/inlet valves and other internal fittings were carried through into the small production run.
 

Photos and Text courtesy of Dr Mike Burchett

The Helmet is made of brass /bronze and has a lifting eye on the top of the bonnet. There are four windows the faceglass being hinged in common with other 3 bolt helmets. There are 2 exhaust valves one is operated by the diver externally by adjusting the black star knob and the other is by the diver pressing his head against a knock valve to the rear of the helmet internally. There is a rebreather canister mounted on the rear of the helmet by 2 connectors and the helmet attaches to the breastplate or corselet by 3 bolts which are hinged on the corselet. There are 4 high pressure cylinders mounted on the diver's backpack and the diver wears a canvas suit which accommodates a lead weight system . He also wears rubber boots rather than the traditional heavy brass toed boots although the rubber boots do have lead inner soles. The outfit is believed to date back to 1958 when it was designed to supersede the Siebe Gorman mine recovery suit. These Heinke outfits were made as prototypes and there were only some 18 made for The Royal Navy . At that time there were still many marine mines located in shipping channels and these outfits were built using anti-magnetic materials The MOD or maximum operating depth was around 60 meters and it used an oxygen enriched breathing gas now known as nitrox with varying concentrations of oxygen depending on the working depth. The diver breathed normally in the helmet without the use of a mask or breathing tube as was necessary in the Siebe Gorman Deep Diving Helmet. Shortly after these sets were produced Heinke was acquired by its larger rival Siebe Gorman and the sets were never produced in commercial numbers.

Photo courtesy of Christies Images Ltd.