I just acquired this bayonet today. I believe it is known as a "mobilization" Polish Mauser bayonet , made at the Radom arsenal in 1939. I have a couple of others that were modified by the Germans by removing the muzzle ring and blueing the piece. This one has a peculiar gray/green phosphate finish on it that I've not seen on a Polish bayonet before. Was it applied by the Poles? Here are some pics.