The prototype NKP 99749, the IM car modeled, was returned empty from
NKP to AC&Y on December 21, 1944... found in a register of cars
interchanged at Bluffton, Ohio (AU TOWER). Many of the NKP 99700-
series appear on other dates. The book doesn't identify the exact
shipper/consignee, but there is sufficient evidence the early NKP
covered hoppers were assigned to Columbia Southern (PPG) at Barberton,
Ohio for soda ash service. The consignee appears to be Ball Brothers
Glass at Muncie, Indiana. PPG was served by A&BB (Akron & Barberton
Belt Line RR), owned jointly by the AC&Y, B&O and Pennsy. AC&Y handled
the lion share of the soda ash traffic. As info. Bob Lucas
The IM car is 99749, in the 99700 series, the first 23 built in 1937
with the small "R" in "Road". (The NKP used the small R, swing tail
R, and even some of the more familiar straight Rs during the immediate
pre-WWII era.) As-built, the first 25 hoppers had the large NYC&StL
above the reporting marks; see page 258 of Rehor's Nickel Plate Story.
(That page also has examples of pre-WWII cars with each type of "R").
The image of the hopper on the IM website does not have the large
NYC&StL, but this car is from the 2nd batch of 25 cars, I don't know
what date they were built off hand, nor how they were lettered.