Have you ever wondered what those white letters and numerals printed on the lens mount of Olympus OM Zuiko lenses mean? Similarly they appear in the film chamber of some OM Camera bodies, but not all. As serial numbers cannot be used to accurately date OM System bodies and lenses, these relatively inconspicuous codes give away tell-tale information as to when an item was manufactured and at which factory it was assembled.
So why does the code appear on some items and not others? For example I have a very old ‘silver nose’ 24mm f2.8 lens and a much later one that I acquired just prior to the OM System being discontinued – the very old one does not bear this code.
Simply put, the answer is location; Camera bodies and lenses manufactured before 1981 have the code hidden and require a small amount of disassembly to find it. In the case of lenses, it lies beneath the rubberised focus collar and is usually found when removing it to tighten the focus ring screws. Early bodies have the code hidden behind the film pressure plate which can be removed by unscrewing the plate from the camera back.
After 1981 Olympus decided to put the code in a more accessible place – whether this was to make the information easily available to techies I do not know but without a little bit of insider information the codes look random. Let’s take a look at the code printed on my late production 24mm f2.8 lens which reads ‘TNT2’; the first two letters are abbreviations for the manufacturing plant. TN refers to the now legendary Tatsuno factory in Japan, and the quality of lenses produced here is highly regarded by photographers around the globe. Olympus still use this factory today to produce their Four Thirds and Micro Four Thirds Optics. The second ‘T’ refers to the year of manufacture with the letter A denoting 1981. Based on this it is easy to count through the alphabet and realise that the year of manufacture is 2001. The number ‘2’ indicates the month of manufacture – 1 being January. So my 24mm f2.8 lens was made at the Tatsuno plant (TN) in 2001, (2) in February (T).
One of my OM4Ti camera bodies has ‘TNT2 04’ stamped in the film chamber; this coincidentally means that the 4Ti was manufactured at the same time as the 24mm, although I do not know what the additional ‘04’ numerals relate to.
Olympus had more than one factory producing their lenses and bodies although the only lens I have bearing a different manufacturing plant was a 200mm f4 that began with the SA code indicating the Sakaki plant was used.
As most of my OM Zuiko lenses have the code printed on the black parts of the mount, I can easily identify their manufacturing date. And the code does seem pretty accurate as it ties in accurately with the date I purchased my lenses. What this shows is that the lenses were not hanging around on dealers shelves for long and may have been ordered directly from Olympus who may have made them to order. An exception to this is my OM3Ti which was produced in 1995 but was not purchased until 2002. I purchased it brand new so it may be that Olympus had just a couple of production runs early in the camera’s life and the high cost contributed to low demand, resulting in them sitting on shelves at Olympus.
Codes are also present on some accessories such as flashguns and teleconverters but it appears that the entire OM System was not coded in this way. For example I have never seen the code on any of the extension tubes or bellows or varimagni finder. Please leave a comment below if you know different!