Like leaves on a tree, serial numbers on consumer goods, while all looking similar, sometimes have subtle variations that can hide interesting information. For example, in the world of classic Chevrolet musclecars (another hobby of the museum curator) from the 1960's and early 1970's, the serial number (VIN) holds interesting information about a car, including its style (sedan, coupe, covertible), year of manufacture, plant where the vehicle was made, and, even a rough idea of when during the model year the vehicle was made based on production figures from the manufaturer.
In most cases, serial numbers on electronic calculators simply start at an arbitrary number, (e.g., 100001), and are sequentially assigned as calculators come off the assembly line. The only information that can be gleaned from such a serial number is perhaps a rough idea as to when the machine was made relative to the start of production, and that's just a guess, because frequently production started off in smaller quantities built per month, and ramped up as production processes were refined, then slowly ramped down as the model was eventually taken out of production. Finding monthly production figures from the manufactures of calculators is very difficult, as there was no requirement to keep such records.
Some calculator manufacturers did encode information in their serial numbers, which can provide some clues about a given calculator, but this information was generally not made public, and finding internal documentation from the '60's and early '70's published by the manufacturers is extremely difficult if not impossible today. Without such documentation, or a large sample of real serial numbers to try to find some kind of pattern in the serial numbers, it is very difficult to decode what secrets might be lurking in a given serial number. One other potential source of information is people who worked in the field at the time, who were privvy to the secrets of the manufacturers. Thankfully, in the case of Sharp calculators, a source was found who provided the keys to deciphering Sharp's serial number scheme.
Sharp calculators produced through at least 1974 had a secret (but not complex) encoding scheme that provided the year and month of their manufacture. This information was useful for service organizations to know when the machine was made, so that they could use this information to determine what engineering or service modifications had been made to the machine at the factory. Frequently after beginning production, calculator manufacturers would find bugs or other types of flaws in the calculator design or construction that they would issue change orders to correct. The change orders (generally called Service Bulletins) would be sent out to field service organizations, requring that when a machine was brought in for service that the modification be made by service technicians. Typically the mods would be eventually implemented in manufacturing, so newer machines would already have the modifications from the factory. The service bulletins would provide an effective serial number or date when the factory modifications began. From this information, a service technician could know by looking at the serial number if it was necessary to make the mandated modifications to a customer's machine when it was in for service.
Sharp Calculators, from the beginning (1964, with the Sharp CS-10A) through at least 1974, had the year and month of manufacture encoded in the serial number. The first digit of the serial number encodes the last digit of the year of manufacture. For example, if the first digit of the serial number is 7, the year would be 1967. If it was 2, it was 1972. This scheme would only be truly uniquely identifiable for the year 1964 through 1973 (4 for 1964 through 3 for 1973), but examples of machines producted in 1974 also have a 4 for the first digit of the serial number. Because of the technology differences that 10 years makes, the date becomes obvious..a machine with vacuum fluorescent or Panaplex displays, and inside has IC's, clearly wasn't made in 1964, because the technology simply didn't exist at that time.
The last digit of the serial number encodes the month of manufacture. Since there are twelve months, and only ten digits available, the letters X and Y are used to encode November and December. The digit zero designates October, while one through nine encode January through September.
The digits between the first and last digits in the serial number represent the sequential unit number of the individual machine. It seems that this part of the serial number started at 0001, 00001, 000001, 700001, or 7000001. As the technology advanced, it was possible to manufacture many more calculators during the lifetime of a model, which is likely why the number of digits in the sequential part of the serial number increased with time. In the early days of Sharp's electronic calculator technology, it was only possible to build perhaps a few hundred machines a month. As IC's and less tedious display technology drastically reduced the complexity of the machines, the time it took to build a single machine fell rapidly, along with ever improving manufacturing processes, thus allowing many thousands of units to be produced during a single month. It appers that the sequential part of the serial number started at a given point, and was incremented for each unit built during the entire production run. There is no information currently known regarding whether the sequential part of the serial number may have any hidden information in it (e.g., whether there is any significance of sequential numbers starting with a seven versus those starting with zero).
For some examples, let's decode some of the actual machines in the museum:
|Model||Serial Number||Decoded Manufacture Date|
|Compet 21 (CS-21A)||605008||August, 1966|
|Compet 20 (CS-20A)||711901||January, 1967|
|Compet 15 (CS-15A)||735305||May, 1967|
|Compet 22 (CS-22C)||811222||February, 1968|
|Compet 32 (CS-32A)||801065||May, 1968|
|Compet 16 (CS-16S)||97016211||January, 1969|
|Compet 363P||27024302||February, 1972|
|Compet 365P||47013104||April, 1974|
Hopefully this information will prove useful to folks to identify when their vintage Sharp calculators were made.