Ex 48-636. This airframe widely quoted as 2520, but that is in error. C-125 c/n 2512 was never built, which means that USAF C-125 batch 48-628 to 48-640 are c/n 2513 to 2525, not c/n 2512 to 2524 as previously thought. So 48-636/XB-GEY is in fact c/n 2521.