Mickey, is the Mauser trademark that of a 'Banner Mauser,' like at the top of the following web page?

http://www.mauserwaffen.de/index.php?id=home&L=1

If so, it could be that the bottom metal is an original Oberndorf sporter type. I don't know enough about them to say if some came with this bottom metal. If so, $400 would seem like a pretty good deal.