You, my friend, are the proud owner of a Weber Smoker Mountain, they are a very good smokers and will produce some very good Q, from cold smoking with an AMNS to pizza and all things in between.
Look on the top vent cover and you will see two letters, then click this link and find out what year you have.
Have fun and don't forget the Q-view.
That is neat, but I just ran out and checked my vent covers (all four) and couldn't find a single letter, which I understand to mean that it is prior to 1979. When my father in law gave it to me about 7 years ago he said at that time it was at least 25 years old, and had never been smoked on still had the booklet in plastic brand new.
Thanks for the link Gene, sorry for the hijack.