SEIKO Original Case Gasket / O-Ring - Ref. EZ2890N – Genuine Seiko Packing (WR)

Original SEIKO housing seal (O-ring) with the correct reference EZ2890N , supplied in the original SEIKO WP spare parts bag (純正部品) .

This is a genuine SEIKO original spare part (NOS) from the historical spare parts supply – not a reproduction and not a universal seal .

This seal is designed for SEIKO enclosures with a precisely defined groove geometry and is typically used as a bottom seal in Water-Resistant (WR) models .

Technical specifications

• Manufacturer: SEIKO
• Replacement part type: Housing seal / O-ring (Packing)
• Part number: EZ2890N
• Shape: Round (O-ring)
• Profile: Standard O-ring
• Material: SEIKO-specified elastomer
• Color: Gray
• Condition: NOS (New Old Stock), unused
• Scope of delivery: 1 piece in original SEIKO bag
• Origin: Japan

Exact allocation & use

The reference EZ2890N belongs to SEIKO's internal packing code system and is case-specific , not universally applicable across models.

Typical areas of application:

• SEIKO WR (Water Resistant) housing
• Vintage and neo-vintage models
• classic screw-in bases without special clamping ring

Use is only permitted if the original part number or housing groove matches .

Explanation of the SEIKO packing coding system

Example: EZ2890N

SEIKO uses a logically structured, multi-stage coding system for seals that clearly describes shape, profile, size and material.

Structure of the part number

1. First letter – Application type / Sealing class

• E = Case Back Packing Seal
  → typical bottom seal for WR housings

2. Second letter – profile shape

• Z = classic O-ring profile
  → round cross-section, no lip or flat seal

3. Four-digit number – size reference

• 2890 = SEIKO internal size code

  • describes the nominal diameter of the housing groove

  • no direct mm measurement

  • clearly within the SEIKO parts system

4. Last letter – Material / Color

• N = grey elastomer

  • good aging resistance

  • dimensionally stable

  • typical for WR cases from the 1970s to 1990s

➡️ Summary:
EZ2890N = grey SEIKO original bottom seal (O-ring) for defined WR housing size.

Assembly and service instructions

• Thoroughly clean the housing groove
• Lightly coat the seal with silicone sealing grease .
• Use without tension
• Do not stretch or twist.

Note regarding water resistance

Installing a new original seal alone does not guarantee watertightness .
Key factors include:

• Condition of base and case
• Glass and crown seals
• professional installation