http://www.gunbroker.com/Auction/ViewItem.aspx?Item=329590778

I think your friend's starting price is a little optimistic, considered that the rifle has been rebarrelled to a screamingly non-German caliber.

Also, referring to the rifle as otherwise original is a little much, considering the dovetail cut in the receiver ring to accomodate the claw mount base.

The claw mount itself is interesting, but I think that finding rings to match the bases would be quite difficult, aside from the misssing lever on the rear (square bridge) base.

That said, it would certainly be an interesting rifle to play with.