The 99 series rifles are no longer made by Savage. In it's day, it was considered a great lever action of unique design. Today, it is considered a classic just like the Winchester 94, and is still a damn fine hunting rifle, especially in the .308 caliber which can hold it's own against many of the modern calibers. Since this gun is no longer being made, it's hard to determine the value. That particular rifle probably didn't cost $600 when new, but if it has had the little use that you described, it may well be worth that price. I had a 99 in .308 about 45 years ago. It was the original design with a rotary magazine (the model C has a clip), and I would jump at the chance to buy another one.