This is the vintage 1990's Citizen Promaster Aqualand, a legendary professional diver's watch C023-089405 model.
Ana-Digi Display: Combines a traditional analog three-hand set with a digital LCD window at the top.
Depth Sensor: The large protrusion on the left side of the case is an electronic depth sensor, which was revolutionary for dive watches when first released.
Two-Tone Aesthetic: The gold-tone bezel, pushers, and crown indicate this is a "two-tone" variant, often associated with the modern JP2004 reissue styling.
Full Lume Dial: The cream-colored face is a "lumibrite" or full-lume dial, designed to glow entirely in dark underwater environments.
Promaster Logo: The "arrow" or "windrose" logo at the center is the hallmark of Citizen's professional-grade sports line.
Water Resistance: Rated to 200 meters (666 feet) or 20 bar
Case Construction: Stainless steel with a screw-down crown at the 4:00 position for analog time setting.
Bezel: Unidirectional, 60-click elapsed time bezel.
Power Source: The original C023 movement typically required three 371 silver oxide batteries to power its diverse electronic functions.
Electronic Depth Meter: Provides constant measurement up to 80 meters (260 feet).
Dive Meter System: Automatically begins measurement when the user reaches a depth of 1 meter (3 feet).
Memory/Logs: Stores maximum depth reached and total dive time.
Rapid Ascent Alarm: Alerts the diver if they ascend faster than 1.5 meters per 10 seconds.
Chronograph: 1/100th second stopwatch measuring up to 59 minutes and 59 seconds.
Daily Alarm: Digital alarm with an "on/off" indicator.
Time Display: Features a 12/24 hour switching function
Calendar: Digital date and day display.
Buttons: Three main pushers labeled "Mode," "Select," and "Set" control the digital interface.
Depth Sensor: Located on the left side of the case, it utilizes a metal membrane and piezoelectric sensor to convert water pressure into depth data.
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