What model Dynaco preamp do I have?

On the rear of the unit it says the Model# is PAS.
That would most likely be a PAS-3X. A very good tube preamp in its day. Lots of modders upgrade them. It's successor, the SS PAT4, was nowhere near as good sonically.
Mabonn, Why would it most likely be a PAS 3X and not a 2, 2X or 3?
Could be any one of those. 3X came to mind because I once had the opportunity to compare a friend's 3X to my PAT-4. That experience is what got me into tubes. I didn't know all those other PAS variants existed.