Heuer. A rare stainless steel automatic calendar chronograph wristwatch with decompression bezel Autavia, Ref 1163 P, Circa 1972Heuer. A rare stainless steel automatic calendar chronograph wristwatch with decompression bezelModel: AutaviaReference: 1163 PDate: Circa 1972Movement: 17-jewel Cal.11 automaticDial: Black, luminous baton hour markers, white outer 1/5th second divisions with orange 5 minute markers, subsidiary dials at 3 and 9 for 30 minute and 12 hour recording, date aperture at 6, orange pointed baton hands with luminous inserts, orange centre chronograph handCase: Brushed and polished tonneau form, screw down back, bi-directional calibrated decompression bezel, winding crown at 9, chronograph pushers at 2 and 4, No.224308Strap/Bracelet: Associated black leatherBuckle/Clasp: Associated steel buckleSigned: Case, dial & movementSize: 42mmThe Heuer Autavia model was first introduced in 1962, the name deriving from a combination of "AUTomobile" and "AVIAtion".The current example is fitted with a rare decompression bezel. This allows a diver to see how long they may stay at a certain depth by aligning the orange triangle on the bezel with the minute hand.