Head-to-Head Comparison

Updated September 5, 2026

Casio G-Shock GA-B2100 CasiOak vs Orient Sun & Moon

Casio's diver meets Orient's dress watch

Quick Verdict

The Casio G-Shock GA-B2100 CasiOak ($100–$150) offers Casio Quartz (Solar-Powered) precision in the tier below the Orient Sun & Moon ($250–$500). The G-Shock GA-B2100 CasiOak measures 45.4mm (48.5mm lug-to-lug, 11.9mm thick) and is rated 200m (20 ATM). The Sun & Moon counters with Made in Japan craftsmanship and 50m (5 ATM) water resistance. Both are exceptional watches for their respective tiers.

CasioG-Shock GA-B2100 CasiOak$100–$150 Check price View the dossier

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Casio

G-Shock GA-B2100 CasiOak

$100–$150

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Orient

Sun & Moon

$250–$500

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Specifications Compared

Feature	Casio G-Shock GA-B2100 CasiOak	Orient Sun & Moon
Price	$100–$150	$250–$500
Case Size	45.4mm (48.5mm lug-to-lug, 11.9mm thick)	41.5mm
Movement	Quartz Module 5689 (Tough Solar + Bluetooth)	Automatic Caliber F6B24
Caliber Type	Casio Quartz (Solar-Powered)	Orient In-House Automatic (Hacking, Hand-Winding)
Power Reserve	About 7 months on a full charge without light; about 18 months in power-saving (Casio)	40 Hours
Water Resistance	200m (20 ATM)	50m (5 ATM)
Crystal	Mineral Glass	Mineral Glass
Case Material	Carbon Core Guard Resin	Stainless Steel
Origin	Made in Japan	Made in Japan

Category-by-Category Analysis

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Design & Aesthetics

Edge: Draw

Casio's design language vs Orient's approach

The Casio G-Shock GA-B2100 CasiOak features a Carbon Core Guard Resin case at 45.4mm (48.5mm lug-to-lug, 11.9mm thick) with Mineral Glass protection. The Orient Sun & Moon offers Stainless Steel construction at 41.5mm with Mineral Glass. Both represent their brand's distinct design philosophy and heritage.

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Movement & Performance

Edge: Orient

Quartz Module 5689 (Tough Solar + Bluetooth) vs Automatic Caliber F6B24

The G-Shock GA-B2100 CasiOak runs the Quartz Module 5689 (Tough Solar + Bluetooth) (Casio Quartz (Solar-Powered), About 7 months on a full charge without light; about 18 months in power-saving (Casio) power reserve) at standard frequency. The Sun & Moon uses the Automatic Caliber F6B24 (Orient In-House Automatic (Hacking, Hand-Winding), 40 Hours reserve) at 21,600 vph (3 Hz). The Sun & Moon offers a longer power reserve.

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Wearability & Fit

Edge: Orient

45.4mm (48.5mm lug-to-lug, 11.9mm thick) vs 41.5mm — different wrist presence

At 45.4mm (48.5mm lug-to-lug, 11.9mm thick), the G-Shock GA-B2100 CasiOak has a bolder wrist presence compared to the Sun & Moon at 41.5mm. Water resistance differs: 200m (20 ATM) vs 50m (5 ATM).

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Value & Cost of Ownership

Edge: Casio

Casio sits in the lower tier

The Casio G-Shock GA-B2100 CasiOak sits at $100–$150 and the Orient Sun & Moon at $250–$500. On the specs that outlast any price: the G-Shock GA-B2100 CasiOak uses Mineral Glass with About 7 months on a full charge without light; about 18 months in power-saving (Casio), against Mineral Glass and 40 Hours on the Sun & Moon. Service intervals are typically 5-7 years for both.

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Water Resistance

Edge: Casio

200m (20 ATM) vs 50m (5 ATM)

The G-Shock GA-B2100 CasiOak is rated to 200m (20 ATM) while the Sun & Moon handles 50m (5 ATM). The G-Shock GA-B2100 CasiOak is better suited for water activities.

Our Verdict

Casio

G-Shock GA-B2100 CasiOak

Choose the Casio G-Shock GA-B2100 CasiOak if you prioritize Casio Quartz (Solar-Powered) engineering, Made in Japan craftsmanship, and 200m (20 ATM) water resistance. At $100–$150, it delivers Quartz Module 5689 (Tough Solar + Bluetooth) with About 7 months on a full charge without light; about 18 months in power-saving (Casio) power reserve.

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Orient

Sun & Moon

Choose the Orient Sun & Moon if you value Orient In-House Automatic (Hacking, Hand-Winding) technology, Made in Japan heritage, and 41.5mm proportions. At $250–$500, the Automatic Caliber F6B24 with 40 Hours power reserve makes it a compelling choice.

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The Bottom Line

The Casio G-Shock GA-B2100 CasiOak and Orient Sun & Moon represent two distinct approaches to fine watchmaking — the Casio bringing Made in Japan tradition while Orient delivers Made in Japan engineering.

Frequently Asked Questions

The Orient Sun & Moon is the better buy if you want a mechanical movement; the Casio G-Shock GA-B2100 CasiOak is the better buy if you want solar power and quartz accuracy with no servicing. For water, the Casio G-Shock GA-B2100 CasiOak is rated 200 m against 50 m, which is the difference between swimming and diving on one side and splashes on the other. On price, the Casio G-Shock GA-B2100 CasiOak sits a band lower ($100–$150 against $250–$500), so it is the cheaper way into the category. Neither is better at everything; the spec table above shows movement, case size, water resistance and crystal side by side so you can weigh what matters to you. We do not test units, so this is the makers' data, not a bench result.

The Casio G-Shock GA-B2100 CasiOak offers better upfront value, sitting a tier lower at $100–$150. However, the Orient Sun & Moon may justify its premium with superior finishing, heritage, or resale value.

Both are suitable for daily wear. The G-Shock GA-B2100 CasiOak at 45.4mm (48.5mm lug-to-lug, 11.9mm thick) with 200m (20 ATM) water resistance handles everyday situations. The Sun & Moon at 41.5mm with 50m (5 ATM) is similarly capable. Both use Mineral Glass.

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How This Page Was Made

Our comparisons are generated from a hand-maintained specification database and reviewed under our editorial standards. We use AI tools to assemble pages from that data. We don’t invent specs: every number traces back to the database, and when we correct an entry, the fix is applied site-wide. As an Amazon Associate, The Horologist earns from qualifying purchases.