Is it a real 35th Anniversary Edition package (not many and very specific features) or one of the thousands and thousands of 99s with 35th anniversary badge on the fender?
The badge on the fender in 99 was very similar to when the 25 Years badge that showed up on 89 and 90 stangs (all cars from April 1989 to end of 1990 production got the 25 Years dash badge - mine has it and was made on last day of 1990 production)