Casio G-Shock GA-100-1A1ER (Nicknamed 'The Three-Eyed Monster' or 'X-Large Combi')
Tool Watch / Ana-Digi (Analog-Digital) Sport Watch · Casio (Casio Computer Co., Ltd.). G-Shock is their premium 'unbreakable' tool-watch line.
Period: Modern Utility (2010-Present). Defined by the 'X-Large' case trend of the early 2010s and rugged tactical aesthetics.
Type
Tool Watch / Ana-Digi (Analog-Digital) Sport Watch
Brand
Casio (Casio Computer Co., Ltd.). G-Shock is their premium 'unbreakable' tool-watch line.
Movement
Quartz Calibre 5081. Features ±15 seconds per month accuracy, magnetic resistance (ISO 764), and approximately 2 years of battery life on a CR1220.
Dimensions
Case diameter: 51.2mm; Thickness: 16.9mm; Lug-to-lug: 55.0mm; Weight: Approx. 70g. It wears very large but is lightweight.
Description
The GA-100 is a cornerstone of the G-Shock lineup, known for its massive 51mm 'extra large' footprint and distinctive symmetric dial layout. This '1A1ER' variant features a blacked-out 'stealth' aesthetic, making it a favorite for military use and streetwear. Its design emphasizes depth and dimensionality through stacked dial components and skeleton hands.
Key Features
1/1000th second stopwatch, speed indicator (Mach), world time for 48 cities, 5 daily alarms, and auto-LED 'Amber' light illumination.
Dial Description
Matte black 'stealth' dial with two digital LCD windows (negative display) and four sub-dials. Features skeletonized tapered hands and 3D applied indices.
Case Material
Shock-resistant black resin (urethane) with a matte finish over a stainless steel inner housing structure.
Crystal Type
Flat Mineral Glass, recessed below the bezel level for impact protection.
Bezel Details
Fixed resin bezel with raised 'PROTECTION' and 'G-SHOCK' lettering; provides 360-degree shock protection for the crystal.
Crown & Pushers
Four large anti-slip resin pushers (Adjust, Mode, Reverse, Forward). No crown; time is adjusted digitally via the module.
Bracelet or Strap
Integrated black resin strap with a double-tang stainless steel buckle for extra security.
Caseback Details
Stainless steel plate secured by four screws. Engraved with 'Casio', '5081' (module number), 'GA-100', and 'Shock Resistant'.
Movement Type
Quartz Calibre 5081. Features ±15 seconds per month accuracy, magnetic resistance (ISO 764), and approximately 2 years of battery life on a CR1220.
Water Resistance
200 Meters (20 Bar). Suitable for professional marine activity and surface water sports, but not for deep-sea saturation diving.
Origin & Provenance
Japanese design; manufactured in Casio’s facilities in Thailand or China (standard for the GA series). Uses an in-house Casio electronic module.
Age Estimate
Circa 2010–Present. This specific unit appears to be a modern production based on the '1A1ER' tag visible in the background.
Cultural Significance
A defining piece of 2010s streetwear culture. It transitioned G-Shock from a purely functional tool into a fashion icon while maintaining its 'unbreakable' reputation.
Condition Notes
Very Good/Excellent. The resin shows minor 'shining' (wear on matte edges) which is typical for G-Shocks. Crystal appears clear. Original packaging (tin/box) is present.
Value Estimate
Retail (MSRP): ~$110 USD. Secondary market: $60–$85 USD depending on condition and presence of the original tin.
Care & Maintenance
Wash with mild soap and water after exposure to salt water. Replace battery every 2 years; check gaskets during battery change to maintain water resistance.
Similar Watches
Casio G-Shock GA-110 (Y-shaped dial structure), GA-120 (Motorcycle-inspired), and the newer GA-2100 'CasiOak' (thinner, octagonal).
Interesting Facts
The GA-100 design was inspired by aircraft instrument panels. It is one of the most successful G-Shock series in history, leading to hundreds of color variations.
Notes
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