Looks to be Oberndorf commercial, but just with the bottom of the 'pear' flattened. I've seen several Rigby rifles with bolts modified in this way.

On another note, I have a Type B in 9 x 57 with a damaged bolt that won't grasp and extract cartridges.There is an Oberndorf sporter bolt available on ebay or gunbroker at the moment. How can I tell whether it will work with the 9 x 57?

thanks