Had a Mannlicher Schoenauer 7mm a few years ago with similar extension, but very neatly welded on, could not tell it was not made that way. Obviously done to ease bolt manipulation, M/S are totally incapable of rapid fire and the flat bolt handles don't help either. The same rifle is now being offered for sale by Rock Island Auction Company, lot 361, February 27-28 Regional Sale. Photo in catalog. Nicely custom stocked too. Have no idea where it has been the last four or five years.

http://www.rockislandauction.com/photos/1014/p_standard/QGM12-C-F2-L.jpg