How to Decipher Seiko’s Case Back: A Beginner’s Guide

Deciphering Seiko’s case back information can be a challenge for the uninitiated. Seiko watches case backs are inscribed with various codes, numbers and letters that can tell you the year and model of the watch, as well as the manufacturer. Knowing how to read the codes on the back of a Seiko watch can help you determine its value, as well as give you a better understanding of the watch’s history.

How to Decipher Seiko’s Case Back 

The case back of a Seiko watch contains a wealth of information about the watch, including the model number, serial number, manufacture date, and more. The case back can also tell you the watch’s type of movement. Knowing these details can help you determine if the watch is authentic and can also help you date the watch.

The model number is the first thing to look for when deciphering the case back. This is usually printed along the outside of the case back and will be in the format of a four or five-digit number. 

The four-digit number is usually the model number for newer watches, while the five is the model number for older watches. Knowing the watch’s model number can help you determine which type of movement is being used and when the watch was manufactured.

The next thing to look for is the serial number. This is usually located in the centre of the case back and will be in the format of either a two-letter code or a four-digit number. The two-letter code will usually indicate the year the watch was manufactured, while the four-digit number will indicate the watch’s production number. Knowing the year and production number can help determine the watch’s age and authenticity.

The last thing to look for is the manufacturer’s marks. These are usually located near the model number and will be in either a two or three-letter code format. These codes will tell you the manufacturer of the watch, which can help you determine if the watch is authentic or not.

Seiko Case Back

Seiko watches have a variety of data shown on the back. This can provide information on the movement type, the creation date of the item, how to open the case, the item’s manufacturer, the case material, and the specific case design code. On rare occasions, when the case back is still pristine, these identification marks are stamped on the exterior.

Most of the information hasn’t changed significantly since the early 1960s, although some data on the rear of Seiko watches have altered.

The internal Let’s Go Suwa No. 160 corporate magazine had extensive information about case backs in 1969. The Seiko Suwa plant published this periodical from the late 1950s until the early 1970s. The website goes into great length regarding all the data that was formerly shown on case backs.

Case Material

The first marking indicates the material used to construct the Seiko cases. Besides the frequently mentioned stainless steel, other materials like ACRP, SGP, and CAP GOLD can also be used. Seiko Case Material Codes contains a comprehensive list of all material codes.

The case number is the following helpful piece of information. There are two parts to this. A 2 or 4-digit Caliber Code comes first (movement number). This is quickly divergent from the Design Code (case type). When combined with the Caliber code, the design code is unique.

For instance, the 8000 cases used with the 5740-8000 and the 6105-8000 are entirely different. The models are distinguished using the fourth digit of the case number. The final number may refer to various distribution points or case design modifications.

Corporate Crest

Behind the Seiko emblem, the Daini “lightning bolt” or the Suwa “typhoon” represent the watch industry. The watch dial will also bear the same marking.

Serial numbers on contemporary Seiko models are six digits long. The first character stands in for the year, the second for the month, and the following four numerals for the particular manufacturing number. Each month is given a number between 1 and 9, with 0 standing for October, N for November, and D for December.

For instance, the serial number for the 7005-8062 casing is 652290. The sample’s unique manufacturing number, 2290, indicates that it was created in May 1976. The distribution of this production volume among the models and manufacturing runs is uncertain.


By deciphering the back of Seiko mod cases, you can better understand the watch you own or are considering buying. Knowing the model number, serial number, and manufacturer’s marks can help you determine whether the watch is authentic and how old. With this knowledge, you can make an informed decision about the watch and ensure you get a quality timepiece.

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