hello all,
although I have just registered here I do have a lot of info to add on this. I am a member of the UKG and am their XO, my forum name is Imp Squipper. Squipper is a term for the military trade of Survival Equipment Fitter which I have been for 26 years. This is indeed a Martin Baker connector, in fact I was only discussing this very connector last week with a fellow UKG member Billy Haggis as I had noticed it in the Star Wars Costumes book and realised what it was. These connectors have been in use in fast jet, rotary and multi-wing aircraft as a means of connecting aircrew Lifepreservers to various items such as ZQ/ZA etc Personal Survival Pack, Irvin GQ Parachutes etc. They are still in-use with us in the Royal Air Force to this day! Now onto the one on the costume, it has been placed front side down with the rear of the connector facing up. The rectangular cut out to the rear is there to house a nut and bolt that passes through, forming a connection method to the Lifepreserver webbing. It has two release buttons which must be pressed together to release the Male portion lug connector, it is designed internally like that as a safety measure ensuring an accidental press of one button will not release the connector from what it is connected to. Hope this helps.
Phil