Check out this custom .350 G&H mauser commissioned for a 1927 safari.
"Griffin and Howe Serial Number 26 in 350 G&H Magnum Custom Built on an original Magnum Mauser action. Left side of the barrel is caliber marked as 35 Magnum. Left side of barrel is caliber marked "35 Magnum. Obviously this has to be one of the first made in this caliber, if not the first. Perhaps this caliber was intended to be a 35 Magnum, but was changed to 350 G&H Magnum so as not to confuse it with the 35 Newton Magnum. This rifle was commissioned by Frederic S. Colburn to be used on his 1927 safari. Also included with this rifle is a book written and privately published by Colburn recounting the details of his 1927 safari in diary format. His PH was none other than, Philip Percival. He writes of sharing camps with Martin and Osa Johnson, George Eastman and others. The book alone is listed on the web from $500.00 on up. This is a great opportunity to pick up a piece with conclusive provenance!!"
http://www.schwandtclassicarms.com/griffin_and_howe_serial_number_2.htm