I've only been to Berlin once, but the current carriages don't look particularly modern. I thought they were probably from the 50s. Evidently not. When were they made?
But yes, there is a lot of different models from different ages, and a lot of them have been refurbished at least once. I'm actually not surprised by this, considering how Berlin is spending billions on a hypothetical airport rather than on its actual trains.
Last time I went to Berlin (Three weeks ago), the papers were baffled to note that among the concerns addressed by the latest series of S-bahn trains, to be phased in shortly, was the doors closing-sound - which has been left unchanged for as long as I can remember (20 years or so.)
:)
Many are made by Bombardier. Bombardier Transportation Global Headquarters is actually in Berlin; see http://www.bombardier.com/en/worldwide-presence/country.germ...