The RG99 hasn't been made in a long time as far as I know. That was a mid-90's model that had 2 siblings, the RG33 and RG66. Was the unti advertised as new or used?
As DTB has said, They stopped making them a while ago, The RG-33 Had dual audio Transistors in push/pull if I remember right. They must have had some stashed somewere??