Beautiful rifle, but the pad is not original to that rifle. I'm not trying to discredit the rifle or put it down in anyway, just stating facts. Like redneck said, the ventilated recoil pads weren't used until after '59. The 1953 supergrade 375H&H had a solid red recoil pad. This is according to Rule: Page 169 of "The rifleman's Rifle" book:
"Recoil pads: There were no changes from those of the standard rifle. The 375 H&H Magnum super grade was phansed out about the same time that the webbed recoil pad was introduced. Since the African lasted through the end of production many of those serial numbered above 460,000 feature the ventilated style."