CB&Q # 49400 - 49799 were built at Havelock ( CB&Q shops in Nebraska ) during 1966 as Class XM-4C. Built to a Northern Pacific design, these were the only boxcars on the Q to feature the waffle pattern on the car side. All of the XM-4C's featured the combination 8 foot and 6 foot plug doors with grain access doors ( at the top of the 8' door ) originally introduced in 1963 on the Class XM-4's. Also like the XM-4's, the XM-4C's had an inside length of 50 foot 6 inch and a 5,080 cu. ft. capacity. While the XM-4B's of 1966 came with roofwalks and ladders, the XM-4C's never received either, even though both groups of cars were being built at the same time. The waffle side cars featured protrusions on the exterior which held load tie-downs on the interior. I received the following from Rupert Gamlen, explaining a discrepancy in the classification of CB&Q 49400 - 49799:

CB&Q # 49400 - 49799 were built at Havelock ( CB&Q shops at Lincoln, Nebraska ) during 1966 as Class XML-11. Built to a Northern Pacific design, these were the only boxcars on the Q to feature the waffle pattern on the car side. All of the cars featured the combination 8 foot and 6 foot plug doors with a grain access door measuring 2 foot 9 inch x 5 foot 6 & 7/8 inch ( at the top of the 8 foot door ) originally introduced in 1963 on the Class XM-4's. Also like the XM-4's, the XML-11's had an inside length of 50 foot 6 inch and a 5,080 cubic foot capacity. While the XM-4B's of 1966 came with roofwalks and ladders, these cars never received either, even though both groups of cars were being built at the same time. The cars were originally fitted with 4 DF-2 belts, and the waffle side protrusions on the exterior held load tie-downs on the interior. Between 1967 and 1970, 126 of them were re-classed XM-4C, presumably when their loading devices were removed. The only exterior differentiation between the XML-11 and the XM-4C is the class stencil to the right of the doors as viewed.