In 1961, Maurice Fenzy patented a device invented by the underwater research group of the French Navy. The device includes an inflatable bag with a small attached cylinder of compressed air. It became the first commercially successful buoyancy compensator. Within a few years, diver throughout Europe, and a few well-traveled Americans, were wearing "Fenzys", an adjustable buoyancy life jacket (ABLJ) which is fitted around the neck and onto the chest, secured by straps around the waist and usually between the legs. They are sometimes referred to as "horse collars" because of their resemblance, and are historically derived from Mae West life jackets issued to World War II flyers.
As they were developed in the 1960s, they have been largely superseded by wing and vest type BCs, primarily because of their tenancy to shift the diver's center of gravity with inflation. The ABLJ's location on the diver's chest means that it does the best job of all BC designs when it comes to floating a distressed, fatigued or unconscious diver face-up on the surface in the event of a problem.