Went to look at a couple Cat Fifteens and one of them has the magneto mounted on the left side. Not sure if the engine was changed out or if they ever offered it like that? The other one has Bishop fenders with a cool looking cowling guard mounted on it. I'm guessing it's after-market I don't think someone would have put the beaded crease and rolled edges on it. They removed the gas tank from under the hood and mounted a square one in that area above the flywheel.
Tom

I suspect the one with a left hand mag is a combine engine. They were made that way so the mag and governor could be got at from the front of the machine.
Bruce P

Has anyone ever seen extra sheet metal like what is mounted on the sides? Was wondering if maybe Bishop also made that.

I saw a similar Cat15 in Oroville, Ca around 2005. My dad Wm. Bishop (son of F.S. Bishop) said the family had a Cat15 with his dad's fenders on it. They farmed citrus and alfalfa with it in Northridge in the late 30's and through the war. Their Cat15 had a shield that was basically an extention of the hood, but not the sides, as shown in your pics. They mounted their toolbox to the back of the top seat to keep it from snaging the low hanging citrus. I still have that tool box somewhere. It still has the brass Bishop fender tag on it. Dad said they repainted their Cat15 with a very brite yellow paint.
It was probably something they had in the shed. SoCal was central to orchard crawler innovations, so anything was possible in those days.