[rotorwrench]

The fact that many model Ts shared a lot of the same parts, makes it difficult to nail down a specific year by characteristics. Some model Ts had the same characteristics for several production years. Characteristics can be used to get a general range of production for the most part. Brass cars of 1916 and earlier are discernible from 1917 through the early twenties cars but there are a lot of subtle characteristics that can narrow this down quite a bit. The 1926 and 27 cars are also very similar but there were enough differences to get a clearer idea of which is which. Ford was always changing things even if those changes weren't all that noticable.

I still don't know anywhere near all the differences but there is a lot of information available to help a person gain the knowledge needed to better ID things from body parts to general chassis parts. Most model T folks don't worry about it too much unless they are trying to be fully authentic in a restoration of a particular year model and body style. Books are available for identification of model T parts so that's a good place to start.