Even though they only had 10 cars with these sides, I'll have to order one.
The CB&Q had a lot of these cars with regular outside-post sides. The 47500-47789 series of 1963 (290 cars, XM-4), 49000-49399 in 1966 (400 cars, XM-4B), and the Q's only waffle-side cars, 49400-49799, also in 1966 (XM-4C, 400 cars).
The XM-4B and XM-4C were built at the same time, but the XM-4B had roofwalks and high brakewheel, while the XM-4C had short ladders, low brakewheel, and no roofwalk. Maybe because the XM-4 and XM-4B were intended for grain service, and the elevator workers needed to be on the roof?
The XM-4 were supposed built from NP plans, but I don't know which series, or how many the NP had.
Any chance of getting them, probably in mass-produced plastic?