While the 30K gallon tank cars are ubiquitous in today's railroading with the transportation of oil and ethanol. There was another 'tank car' that circulated around Pittsburgh when it was the steel capital of the US. The Linde liquid oxygen tank cars that looked like box cars as consequence of all the insulation necessary to maintain oxygen as a liquid. Frequently saw them on B&O trains operating on the P&W Subdivision when I was a Train Order Operation in the Summer of 1967.
