Assuming you still need a value, ask the folks over at Target Talk forum. I think it's the most popular Olympic shooting forum here in the US.
FYI, that looks like an 1807 barreled action in a 1813 free rifle stock. The 1807 rifle is considered a "Standard" rifle. A free rifle stock is worth more, so that should help with value. The thing is, is that stock looks knocked about quite a bit.
Scott