I've been perplexed for a number of years by several tank car photos I've scavenged for possible future models (Yeah, right!). Today I spent a couple of hours playing detective, and can offer the IDs for three tanks that were a mystery to me.

CMTX 465 probably belongs to "John Shatford, Agent". These marks were in use from 1935 to 1947, but they were used for other operators after our period of interest. Information on this car comes from Ian Cranstone's pages, which have a huge list of private reporting marks.

QTX 106 is from Quaker City Tank Line. Actually, if I had blown this up to gragantuan size sooner, I would have seen "Quaker City Tank Line" on the right side of the tank. (Sigh!) QTX was used between 1930 to 1932, and again in 1935 by General American. 

Finally, we have TKX 700. This car belonged to Thomas Keery Co. Their fleet cas active under these marks from 1920 to 1935, and again from 1937 to 1945. I found their listing, including this very car, in a 1937 ORER online. Sadly, Google Books only allowed a partial view of the page, and information about the ownership and home yard for their fleet was cut off. I was able to discover that Keery apparently refined phenols, esters and other chemicals from coal tar. Patents in this company's name are recorded for the phenol refining process.