Nice auction find.......don't get caught with it.....
 

On the front anyway....

Obviously a rifle mounted dagger, but what does it go on, and what country of origin?

This is a rare marked one
Germany used a wide variety of bayonets on the Mauser Gew-8 and Kar-98 rifles. They entered World War 1 issuing the 1898/05 or ‘Butcher Blade’ model. As the war progressed the shorter blade types and the ersatz models were introduced.
A small percentage of German bayonets were made with a saw back. They were only issued to noncommissioned officers or pioneer troops.....about 6%