THE AUDITORY TANK - Those were times of the manual reserve, a metallic pole to pull and free the remaining 20 or 30 bars of residual air in the single tank when breathing was becoming harder, sufficient to calmly ascend to the surface. To avoid dangerous divers’ distractions and alert companions of the air end, here it comes the auditory reserve, a contraption installed inside the tank to be used as a bell. This sound gave the alarm by reproducing it in the surrounding water. It seems that this sound attracted fishes. See and believe in U.S. Divers catalogue of 1963, available in this website.
THE POCKET GAFF - It was invented in 1968 by Mr. Gengarelli, tired of the obstacle of the standard rigid and long gaff, fussy to keep in the rubber boat and uncomfortable to bring during the dive, where sometimes it was needed to extract preys from their lair. This new gaff was made of small steel bushes, linked by a steel core housed in a pocket case of 11,5 x 17 x 1 cm. Once rigidly blocked, it had an extension of 85 cm.