The upside down K would be correct for a USGI replacement stock. It sounds like an arsenal rebuilt rifle, but the majority of A4's have been rebuilt, so that is not a bad thing.
BUT, if it was installed at US arsenal, it should also have an arsenal stamp & proof P on the grip.
I think the price is in the middle of the current price range. If it has a correct 330C, M73B1, M8, or M84, AND the correct USGI mount & rings, it is a good buy. If not, it's probably about $600 too high.
If you aren't sure what you are looking at, you want to post photos for us.
Neal