That appears to be a later Mauser (or possibly Menz?) DSM, as Bob said. Perhaps the bolt was missing or broken at some time; it looks like someone welded a different handle onto the bolt, and customized something for a broken or missing shroud and safety. I know of no makers who produced anything that looks quite like that. A photo of the bolt OUT of the rifle would help, but may not tell a person any more than it being a do-it-yourself repair job.
Steve