Thank you very much for this information Craig!
The puzzle is nearing completion.
If only I could find out what was stecilled on those domes!
Resumé: these 1930-built, 10,000 Gallon insulated double dome cars were in service as NIPX #6, 7 & 8 for the North Indiana Public Service plant in Michigan City, Indiana.
They were already out of the ORER in 1936.
#8 was possibly the only only surviver (the other 2 possibly went back into the GATX pool) at the NIPCO plant as 'captive car' and was photographed there by Arnt Gerritsen.
Who also made drawings of which Overland made a model in ca. 1991.
Pity they didn't issue a painted & letterd version, otherwise it would have been on the BT files as sample for mine.
Now the real challenge is to find the original Arnt Gerritsen picture of NIPX 8, so I can make some decals for it.
In my closets this car is a sample of a lost car, far away from home in 1950 in the Feather River Canyon.
To return home after decades, just in time for Arnt to take pictures of it around 1988.
I understand from Jeff Lemke the OMI model is from 1991.