Attached are the photos of NALCO cars I have found online (besides the ones you and Steve posted).
According to a 1966 ORER, Nalco owned 18 such cars numbered 101, 103-105 and 108-121. Here is a shot I found of 120 working on the Rock Island in Peoria.
The tank cars appear to be a mix in both shots including a UTLX car behind 120.
It is not clear when these cars were first used, but the NALCO name apparently arrived circa 1959 shortened from National Aluminite Company, according to Wikipedia.
From: main@RealSTMFC.groups.io [mailto:main@RealSTMFC.groups.io] On Behalf Of Doug Forbes
Sent: Sunday, November 10, 2019 11:13 PM
Subject: [RealSTMFC] Nalco Weed Sprayer and tank cars
I am looking for help in potentially modeling this Nalco weed sprayer train that was running on the C&EI in 1959 as photographed by J. Parker Lamb. I am looking for ideas on a good HO scale starting box car to modify into the weed sprayer as well as who might have owned the tank cars (I think Nalco owned them from other research I found) what would be good starting models for them as well. I'm looking for any guesses or hunches or commentary you might have.
Thanks to all!