I believe this is a 357 pellet gun that has been modified to fit a 3357 spot marker barrel/front end, although I am far from an expert on this matter.
The marker is in working condition and does fire the little .50 cal paintballs pretty well. However, the two ammo drums have some wear on the teeth causing them to occasionally slip the rotating mechanism
asking $100
Larger/higher resolution pictures can be found at
Synergyseller Stuff