Seiko Original Gasket (1 piece) – Ref. OH2300B01 - 768 - NOS

This original Seiko gasket is from old stock (New Old Stock) and was originally supplied by Hattori Seiko Co., Ltd. in Japan. It serves as a case gasket (O-ring) to seal the watch case and is specifically designed for classic Seiko models with the corresponding case dimensions.

Technical specifications

• Manufacturer: Seiko (Hattori Seiko Co., Ltd.)
• Part number: 768 - OH2300B01
• Component: Case Back Gasket
• Cross-section: round (O-ring)
• Color: black
• Material: original Seiko specification (synthetic elastomer, factory defined)
• Condition: NOS (unused, original packaging)
• Scope of delivery: 1 piece

Dimensions (decoded from the part number)

• Inner diameter: 23.0 mm
• Material thickness (width): 0.50 mm

These dimensions are crucial for proper sealing and should be adhered to exactly.

Explanation of the Seiko seal code OH2300B01

Seiko uses a systematic coding scheme for its seals. The part number OH2300B01 can be broken down as follows:

1. O – Cross Section

→ Round profile / O-ring

2. H – Latitude or Thickness Code

→ 0.50 mm material thickness
(H-code corresponds to a thickness range of 0.50–0.59 mm)

3. 2300 – Size code

→ 23.00 mm inner diameter
(Measurements always given in 1/10 mm increments)

4. B – Color code

→ Black

5.01 – Serial or revision number

→ Internal Seiko reference (no change in dimensions)

In summary:

Black O-ring seal, 0.50 mm thick, 23.0 mm inner diameter

Typical use

• Seiko vintage watches
• Housing bases with approx. 23 mm sealing seat
• Classic hand-wound and automatic models (depending on the model)

⚠️ Note: The exact model assignment depends on the specific housing. A dimensional check is recommended before installation.