Yes your bolt has been set up for a rimmed cartridge by the look of it and the extractor blade will be hardly long enough (looks short in the photo) to enter the case head extractor groove and grab the rim of the rimless 350 Magnum case, hence probably the reason it has broken some of the blade off.
My Mauser bolt face shown below has been opened up from the smaller 10.75 Mauser rimless for the larger 404 Jeffery case which also being rimless did not need any alteration to the extractor other than stoning the blade toe a bit to allow a cartridge head to feed up onto the bolt face behind the blade.