Date codes

Most collectors of early electronic calculators will sooner or later ask themselves: „How old is this piece of history in my hands“? The answer is quiet easy, in conjunction with the pictured albums here in the Datamath Calculator Museum you get a rough estimate of the timeframe each calculator was built. Some models had a very short lifetime, e.g. the rare SR-16 was manufactured between October 1974 and early 1975. Other calculators stayed longer, the famous TI-68 was introduced 1991 and was available in some countries till the year 2000. If you inspect the calculators manufactured by Texas Instruments carefully you will notice small numbers stamped with ink on the body shell, embossed in the plastic mold or printed on the license plate. These numbers look typically like 314, 2676 ATA or I1090. If you study this article carefully you’ll learn that the first calculator is a Datamath Version 2 manufactured April, 1973, the second calculator was produced in the Abilene, TX facility and the third is a modern, Taiwanese LCD calculator. Interested in getting more information?

• Search the numbers

Starting with the introduction of both the Datamath and the early Desktop calculators Texas Instruments used visible ink to stamp the manufacturing date on the back of the calculator housing using a 3-digit code. Unfortunately in most cases the ink got lost over the time on the polished surfaces of the early calculators. Later models like the TI-2550 or Exactra line used a structured surface and the ink is more durable. Some calculators like the SR-50 got the date code printed on hidden places like the internal plastic frame below the battery pack. If you can read only parts of the numbers you should open the calculator and search the manufacturing date on the integrated circuits to limit the possible date range. Calculators introduced in the year 1976 or later use another coding with 4-digits embossed into the mold of the rear case shell. This method was durable, in some cases the readability is limited due to bad adjusted temperature or pressure of the tooling. With the TI-1750, the first Texas Instruments calculator produced in Japan another coding scheme using 3-digits was introduced. These early LCD-calculators with their metal housing got small adhesive license plates carrying the model designation, serial number, date and origin of manufacturing. Later far East products use a novel 4-digit coding for the date of manufacturing.

• Decipher the code

You should be able to decipher 5 different coding schemes of the manufacturing date to cover all calculators and related products manufactured by Texas Instruments. In addition you get in most cases the information of the place of manufacturing.

3-digit date code

Early calculators introduced between the years 1972 and 1975 make use of a three digit code to define the week and year of manufacturing.

Example:  314 reads as 31^th week of the year 1974

You notice immediately that this code was not Y2K compliant and there was a need for another coding scheme.

The origin of the calculator is usually Dallas, TX if not otherwise noted. Only the TI-2500 / TI-3500 was reported to be produced in Italy, UK and Spain and the SR-10 / SR-11 in Brazil and Spain.

3-digit "Early Far East" date code

Calculators produced in Far East and Southeast Asia during the late 70s and early 80s use a three digit code to define the month and last digit of the year of manufacturing

Example:  104 reads as October 1984

The manufacturer of the calculator is coded with one letter and the origin written in plain words. A table is given with the 4-digit "far East" code.

4-digit date code

Calculators introduced later than 1975 and not produced in Asia use a four digit code to define the week and year of manufacturing.

Example:  2676 reads as 26^th week of the year 1976

The origin of the calculator is coded with three letters and / or written in plain words.

4-digit "Far East" date code

Calculators produced in Far East and Southeast Asia use a four digit code to define the month and year of manufacturing.

Example:  1090 reads as October 1990

The manufacturer of the calculator is coded with one letter and the origin written in plain words.

6-digit "European" date code

Calculators produced in Italy use sometimes a six digit code giving the day of production.

Example:  RCI240595 reads as May 24, 1995

3-digit "European" date code

The years 1990 and 1991 are encoded with the digit 0 resp. 1.

5-character "Early Hewlett Packard" date code

Example:  2219S reads as year 1960 + 22 = 1982, week 19 and manufactured in Singapore.

5-character "Later Hewlett Packard" date code

Example:  ID912 reads as manufactured in InDonesia in the year 1999, week 12 and manufactured in Singapore.

3¼-character "Radio Shack" date code

Example:  1A5 reads as 1^st month 1985 or 1995. The character A is just serving as a separator between month and year.

4-digit "Integrated Circuit" date code

Most Integrated Circuits (ICs) manufactured by Texas Instruments or Toshiba use a four digit code to define the week and year of manufacturing.

Example:  7424 reads as 24^th week of the year 1974

The origin of the IC is written in plain words. Early Texas Instruments ICs manufactured by Texas Instruments using a metal–oxide–semiconductor (MOS) process, use a TMS designation and we learned from the TMS1000 and TMS7000 documentation the TI Standard Symbolization: TMX, TMP, and TMS are representative of the evolutionary stages of product development from engineering prototypes through fully qualified production devices:

Devices with on-chip ROM (Read-only Memory) usually include a Cxxxx or CDxxxx reference and might have two different © information:

3-character "Japan Integrated Circuit" date code

Most integrated circuits (IC‘s) manufactured by Hitachi and some other Japanese companies use a three digit/letter/digit code to define the year, month and week of manufacturing.

Example:  3B4 reads as 4^th week in February of the year 1973

The origin of the IC is written in plain words.

4-character "Sharp Integrated Circuit" date code

Most integrated circuits (IC‘s) manufactured by Sharp in the 1980s use a four character code to define the year, month and week of manufacturing.

Example:  538A reads as 1^st week in August of the year 1983

• UL Listed?

If the nameplate of a desktop calculator carries the round UL mark it was tested according to the UL Standards common in the United States. And just this little logo on the nameplate spills out the secret! Every company submitting a product to Underwriters Laboratories Inc. (UL) receives an UL-File Number like E12345. Driven by the wide usage of the Internet the www.ul.com website provides the service of online access to the UL Certification Information. Follow this link to the database of UL certified desktop calculators from Texas Instruments. It reveals a lot of surprises.

This mark is a registered trademark of Underwriters Laboratories Inc.

• Reworker or repaired?

If you compare the salary of an employee and the price tag of an early calculator you will understand that between 1972 and around 1976 defective calculators were repaired. Usually these products carry a small label „reworked“. Another circumstantial evidence could be found in the relation between the calculator manufacturing date and the age of the integrated circuits inside. During the calculator war the companies had trouble to produce enough calculators for the market. The typical difference between the IC manufacturing and the calculator production was 4 to 8 weeks. If you notice an IC newer than the calculator you have a reworked calculator. On the other hand, if you notice an IC much older than the calculator this one was produced at the end of its lifetime.

If you have additions to the above article please email: joerg@datamath.org.

© Joerg Woerner, 2001 - 2021. No reprints without written permission.