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how can I determine the age of an olympus om lens from the serial number?
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Determining the exact age of an Olympus OM Zuiko lens based only on the serial number can be difficult, as Olympus did not publish a universal, publicly available serial number to production date chart for their OM lenses. The serial numbers are typically sequential, but there's no single, known decoding scheme for the full number.
However, there are a few other codes and clues that can help you determine the approximate age and version of an OM lens:
1. Hidden Production Date Code (More Reliable for Date)
For many later OM System lenses (generally those made after 1981), Olympus began stamping a small, two-letter, two-digit code on the lens mount or beneath the rubberized focusing grip.
The format is typically A B Y M, where:
A B (First two letters) is the manufacturing plant (e.g., TN for Tatsuno, Japan).
Y (Third character - a letter) is the Year Code. It starts with A = 1981 and cycles through the alphabet (excluding some letters like I, O, Q, etc. in some years).
A = 1981
B = 1982
C = 1983
...and so on.
M (Fourth character - a number) is the Month Code (1=January, 2=February, etc.).
Note: You may need to carefully peel back the rubber focus grip or look very closely at the base of the lens mount for this code. It's often very small.
2. Serial Number as a General Indicator of Version/Era
While a direct date conversion isn't possible from the full serial number, the serial number can sometimes indicate a specific, often optically improved, version of a popular lens, which places it within a certain era.
Example (50mm f/1.4): The later, generally preferred, multi-coated version is often cited as having a serial number greater than 1,100,000 (or 1.1M). This places it in a later production batch.
3. Lens Name and Cosmetic Clues (Indicates Era)
The inscription on the lens can help classify it into a general production era:
| Inscription (on lens front) | Approximate Era | Coating Status | Elements in Design |
| G. Zuiko, F. Zuiko, etc. (single letter prefix) | Early OM (c. 1972-mid 1970s) | Single-Coated | The letter (e.g., G for seven) indicates the number of lens elements in the design (a mnemonic code). |
| MC Zuiko (often preceded by the element letter, e.g., MC G. Zuiko) | Mid OM (c. mid-1970s) | Multi-Coated | Uses the same element-count prefix. |
| Zuiko (No letter prefix, just "Zuiko Auto-T" or similar) | Late OM (c. late 1970s-End of Line) | Multi-Coated (Newer/Improved) | Indicates the final, most modern coatings (often marketed as NMC - New Multi Coating). |
You can often find detailed information, including known serial number ranges for specific versions, on dedicated Olympus OM fan and collector websites.
Gemini can make mistakes, so double-check it