The Army Gazelle fleet included the aircraft for the Royal Marines (3 Brigade Air Squadron as was).
The RM Gazelles had SAS fitted presumably for reduced workload on over water ops.
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Crab, I was on Gazelle Conversion Course No 7, in 1974, as a Royal Marine, and during the 3 years that I flew the Gazelle we never had SAS fitted. We also did a deployment to the USA on HMS Hermes, (or was it Bulwark?) the following year, 1975, and night deck landings mid-Atlantic were very interesting in a machine without stabilisation - you almost didn't dare blink until you were on finals!
Sounds like it was a good bit of kit for a single engined helicopter.