In over 30 years flying, including seven fighter types, the only non-martin baker seat I sat on was in the Gnat. I seem to remember a unique safe seat arrangement that replaced the use of safety pins with a simple 'head knocker'. Hard to forget to put the seat to live because it would remind you by hitting the back of your head whenever you put your head up straight. The safety record of the seat was also pretty good as I remember it.