The best I can find is 1995-1997 if you go to PSE's website and go to product support you can go under bow specifications... http://tune.pse-archery.com/
I just typed force in the keyword and clicked search... How much is the person asking for it would probably be the most important question. Old bows have been killing nice bucks for years but there have been a BUTT-LOAD of advances in speed, accuracy and weight that will make you a better shot in the last 4-5 years. So unless it's a great deal I would probably put a few more bucks to it get something a little newer because you may have to put money into this bow anyways for strings and cables???