Nothing specific, but on the Steam Freight Cars forum there has been occasional discussion about standard tank cars converted to two- or three-compartment cars. This was done by adding internal heads and adding a dome for each new compartment. The original dome, sized for the entire original tank, stayed in place and a new, smaller, dome was added for the new tank. In this case, it looks like the tank was split two-thirds/one-third or thereabouts. It was probably more common, based on photo evidence, to turn a car into a three-compartment tank, but I believe this configuration has been documented as well. I don’t recall if there are any specific documents on this conversion, other than photos that have turned up. Needless to say, this was relatively rare. Best guess is the twenties and thirties are when this might have happened.

One possible reason this was done was for delivery to smaller customers, who might receive shipments of (I’m hypothesizing here) kerosene and motor oil, but didn’t want to order either one by the carload. By the time I came along in the late sixties, it was likely that such smaller customers had mostly been switched to truck delivery.

Hope this helps.

RG7