Deciphering SEIKO Part Numbers

SEIKO Coding Document Transcribed

• Original Scans
• Crystal Part Number Coding
  • Round-shaped Crystals
  • Other-shaped Crystals
• Gasket Part Number Coding
• Crown Part Number Coding

World Time Watch Part Numbers

• Part Numbers by Model Number

SEIKO Coding Document Transcribed

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First, here are the source documents:

The following text has been modernized, reformatted and re-purposed from the document scans above. Most of the wording is lifted from the originals, updated and corrected as errors are found.

Crystal Part Number Coding

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The structure of the parts number for the glass is classified into two groups according to the shape of the glass, that is, whether the glass shape is round or not.

Round Glass (10 digits)

Round glass / crystals are codes in the following segments:

NOTE: In the coding system for glass, type code and finish code have been revised from 1990 for new models. The following examples show the pre-1990 and post-1990 coding changes.

Size Code

The Size Code shows the glass diameter in three numerical digitals. For Example:

Type Code

The Type Code is expressed in one letter.
-OLD-

-REVISED-
The following two letters are newly used to identify the mounting structure of the glass. "N" and "W", which were used so far to denote the water resistant quality, have been replaced by the new classification.

• A: Bonded
• P: Pressed in using plastic gasket

For Example

NOTE: "N" and "W" will still be used for glasses having other types of mounting structure such as welded glass.

Serial No. Code

A number from 01 to 99 is assigned for the purpose of production-related classification.

Material Code

Expressed in one letter, as follows:

• A: Acrylic glass
• E: Acrylic glass/others
• G: Hardlex glass (Inorganic tempered glass)
• H: Hardlex glass (Inorganic tempered glass)
• J: Hardlex glass (Inorganic tempered glass)
• K: Hardlex glass (Inorganic tempered glass)
• L: Hardlex glass (Inorganic tempered glass)
• S: Sapphire glass
• Z: Others

Finish Code

Expressed in one letter, as follows:

NOTE:

1. * .......... A numeral (from 1 to 9) or a letter of the alphabet (M, V, H, J, R and S) is assigned in the order in which the code is established.
2. Curved glass (K) and cut glass (C) are newly classified as ordinary glass (N).

Color Tone Code

Expressed in one letter, as follows:

• M: Green
• L: Blue
• P: Pink
• V: Violet
• Y: Yellow
• O: Transparent
• S: Transparent w/ silver color ring
• G: Transparent w/ gold colored ring
• E: Others

Shape Code

One letter to show the cross section of the glass.
There are a great variety of cross sections, and the following are typical examples.

Sub Code

One numerical digit to show the slight difference in color tone.

Shaped other than round glass (10 digits)

The first three digits have a different meaning from those for the round shaped glass.

NOTE: In the coding system for glass, type code and finish code have been revised from 1990 for new models. The following examples show the pre-1990 and post-1990 coding changes.

Shape Codes

Expressed in two letters to show the plane view of glass.
The following gives typical shapes.

Serial No. Code

A number from 0 to 9 is assigned for the purpose of production-related classification.

Gasket Part Number Coding

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Gasket codes are classified into three groups as follows:

1. Non plastic gasket (9 digits)
   1. Previous coding system
      The 3rd and 6th digits are numerical in the previous system.
   2. New coding system
      The 3rd and 5th digits are numerical in the new system
2. Plastic gaskets (8 digits)
   1. Coding system of "OTHER CASING PARTS" on page 14.

Previous Coding System (9 digits)

Cross Section Code

One alphabetical digit to show the shape of the cross section

Width Code

One alphabetical letter to show the cross section width.

Example values are:

• A: 0.60mm
• B: 0.75mm
• C: 0.90mm
• D: 1.05mm
• E: 0.85mm
• F: 1.30mm
• G: 0.40mm
• H: 0.50mm
• I: 0.55mm
• J: 0.80mm

Size Code

Four numerical digits to show the inside diameter of the gasket between 9 o'clock and 3 o'clock sides.

Example values are:

• 2980: 29.8mm
• 2920: 29.2mm
• Etc.

Color Tone Code

One alphabetical letter to show the color of the gasket, as follows:

• B: Black
• L: Blue
• N: Grey
• O: Transparent
• W: White
• Y: Yellow
• E: Others

Shape Code

One numerical digit to show the plan view of the gasket. If a parts number is given 7-digits, the shape code is omitted.

Serial No Code

A number from 1 to 9 assigned to differentiate the shapes and materials. In cases with 7-digit notation, the serial no code is omitted.

New Coding System (9 digits)

The new coding system retains the previous codes for the following:

• Cross Section Code
• Color Tone Code
• Serial No Code

Width Code

Example width code values for the new coding system are as follows:

• A: Less than 0.19mm
• B: 0.20 - 0.29mm
• C: 0.30 - 0.39mm
• D: 0.40 - 0.49mm
• E: 0.50 - 0.59mm
• F: 0.60 - 0.69mm
• G: 0.70 - 0.79mm
• H: 0.80 - 0.89mm
• J: 0.90 - 0.99mm
• K: 1.00 - 1.09mm
• L: 1.10 - 1.19mm
• M: 1.20 - 1.29mm
• N: 1.30 - 1.39mm
• P: 1.40 - 1.49mm
• R: 1.50 - 1.59mm
• S: 1.60 - 1.69mm
• Z: More than 1.70mm

Size Code

Example size code values for the new coding system are as follows:

• 298: 29.8mm
• 012: 1.2mm
• 007: 0.75mm

Shape Code

Example shape code values for the new coding system are as follows:

• A: Circle
• B: Square
• C: Rectangle
• D: Gable (generally triangular)
• Z: Others

Material Code

Material codes are missing the scanned source documents and images. If you have a copy of this missing information, please reach out!

Crown Part Number Codes

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There are old (8 digit) and new (10 digit) coding systems.

Old 8-Digit Codes

Size code

Two numerical digits to show the outside diameter of the crown.

Type Code

One letter to designate the crown function

Serial No code

A number from 01 to 99 is assigned to differentiate the appearance.

Finish code

Expressed in one letter to desgnate the surface finish of the crown.

• N : Ordinary finiah
• D : Diamond-cut finish
• E : Others

Color tone code

One letter to show the material and the kind of surface plating.

Assortment code

One numerical digit or letter to show the type of marking on the crown.

New 10-Digit Codes

Screw diameter code

A numeral to identify the type of screw that fits the winding stem.

• 1 : No screw
• 6 : 60P15
• 8 : 80P20
• 9 : 90P22.5

Type code

A letter excluding I, O, Q and U to classify the type of crown.

Size code

The first two figures of the outside diameter of a crown.

Serial No. code

Consisting of two digits; a letter excluding I, O, Q and U for the first digit and a numeral for the second digit.

Material code

A letter excluding I, O, Q and U to denote the material of the crown head.

• B : Brass
• K : 18K (* Color of gold is classified by the color tone code.)
• M : 14K (* Color of gold is classified by the color tone code.)
• N : Ns (Nickel silver)
• P : Plastic
• S : Stainless steel
• T : Titan
• Z : Others

Finish code

A letter excluding I, O,Q and U to denote the finish of the roulette and head of the crown.

Color tone code

A letter excluding I, O,Q and U to denote the color tone of the crown head.

Sub code

Consisting of a numeral and a letter excluding I, O, Q and U that denote the difference in color tone, material and color tone of jewel and marking. The numeral is assigned in the order in which the code is established.

World Time Part Numbers

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The following parts charts are focused on consumable parts, like gaskets and crystals. Click on the model no in the first column to open a new tab to the Jules Borel database, which contains additional part numbers.

Generation 1: Mechanical Watches

Generation 2: Digital Watches