Royal Aircraft Establishment Negative No. 32938. This is a b+w glass transparency (slide) with card edges. Approx. 8x8cm (3x3"). The image shows 2 airmen in uniform within some form of compression chamber. Both are wearing headphones and type-D oxygen masks with type 19 microphone assemblies. The masks are being used with an unusual head-harness. One man is operating a aircraft gun - apparantly 'firing' at some kind of electrically wired 'target' a few feet ahead of him. The second man is operating some form of equipment relating to the target/gun. Both men have medical branch collar dogs. I would assume that the slide was used as part of some oxygen deprivation testing or similar. Very interesting image. Stock code P14459.