By Cox & Stevens Aircraft Corp. Load adjuster for the B-17E & B-17F 'Flying Fortress' bombers. Looks similar to a conventional slide rule but was used to ensure the correct weight distribution throughout the airframe depending on the amount of fuel, bombload etc. A bit grubby and with minor loss of the white plastic 'coating' in places (see photos). Also lacks the sliding 'cursor'. Complete with fully marked leather case. Stock code M16772.