Definitely a Borchardt C93. Don't know about the shoulder stock, I have never seen an original for a Borchardt, just photos. Last fleeting glimpse of one I saw, the price was into serious money, north of the $30,000 mark. Check out this site, they had one for sale, perhaps they can advise.
http://phoenixinvestmentarms.com/His...rchardtDWM.htm