Developed by Art Mashburn during the 40’s or 50’s. The rifle below was featured in Heritage Auctions LOT #32616 with the following notes:

“…nickel plated floorplate engraved with a charging Grizzly bear in relief by Dan Clark. Nickel plated grip cap engraved: Warren Page by Mashburn Arms Co…  Four photos of Arthur McGreevy and Martha Page with the rifle at the 6th International Hunters & Fishermen’s Conservation Conference when McGreevy purchased the three Mashburn rifles. An unsigned parchment stating: “Warren Page owned and used a great many rifles in his hunting life. The .35 Mashburn Magnum was special. It was built by a friend for a friend, and for a specific purpose: hunting the great bears in the most demanding circumstances.”
Provenance
The rifle was featured in an article (Field & Stream January 1970) – Nothing’s Wrong with Nanook about a polar bear hunt where both Page and McGreevy used the rifle after McGreevy’s gun froze up.