I wouldn't let the lack of knee controller be a deal breaker. IMO it's still a decent price even with having to clean up the wiring. The case looks like it's in decent condition, the missing slide plate will add another $5-10 to the final cost but at least you can still get them. But then I have a serious weakness for 99s and other 3/4 size machines. OurWorkBench's guess looks pretty close to right on the age to me too. I was given a very similar one from that time frame by Cari here.
Rodney