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.
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.