You might not be interested in knowing the exact age of your cameras but most collectors are. Having a precise date is good but no always possible.
The dates that cameras were made between can be ascertained from promotional literature and catalogues. The British Journal of Photography Almanac has adverts for many camera models – these do not actually date the camera but if a camera is advertised in, say, 1954 then it musty have been available in that year. The Almanac also has a section called New Goods which does date the introduction of a particular model.
A London retailer – Wallace Heaton – published a catalogue from 1938 to 1972 called the Blue Book (because of its cover). Again, a camera model being advertised in this does not precisely date the camera but does show that the camera model was available in that year. Other retail catalogues can provide the same information. Manufacturers’ catalogues can provide more precise information as they will announce new models.
There are two tomes of use to collectors: McKeown’s and the Hove Blue Book. These give the dates that a camera was produced but with the caveat that both contain mistakes.
Serial numbers can be very useful for dating individual cameras. There are limits to this, however. Some makers, usually of cheaper camera, did not use serial numbers. Most makers did use serial numbers but which serial numbers were used when has never been made public. Some markers, Kodak and Hasselblad for instance, used code words to date their cameras. I have some useful tables of serial numbers available here.
Some, but not all, Soviet makers start their serial numbers with the year of manufacture. It is difficult to tell which serial numbers have the date and which just start with digits which could be the date but are not.
Some serial numbers have well established serial number date ranges – Carl Zeiss lenses and Schneider lenses for example. Some serial number date ranges have been meticulously assembled by camera enthusiasts – Zeiss Ikon, for example, and Nikon. Some makers, Zeiss Ikon and Voigtländer are examples, used the same serial number sequence for all their output while others, Nikon for example, have separate serial number ranges for each model.
When you have a camera with a body serial number, shutter serial number and lens serial number, you would hope that each would give the same date but this is frequently not the case. The main reason for this is batch manufacture. Firms like Zeiss Ikon would make a large batch of a particular body moulding and then use that batch of mouldings over many months. They would buy in batches of shutters and lenses and, again, use each batch over many months. This can result in bodies, shutters and lenses being assembled into a finished camera with the components dating from different years. When this happens, I assume that the date of manufacture is the most recent of the three.
There is another reason for a mismatch of serial number dates and that is repair/update. For repairs, either the lens or shutter might be replaced several years after the camera was originally made. Other than repair, the owner might upgrade either shutter or lens when finances allow. When this happens, one of the serial numbers will be significantly out of step with the others. This can happen today with a repairer having no source of new components having to cannibalise old cameras to get the parts for the repair. This might result in components being several decades out of sync.