The TM8 tank cars held 8,000 gallons and had a weight of 39,000 lbs. General classification was TMx, where x indicates the number of thousand-gallon capacity of the car. The TM8's were built in 1916 by the American Car and Foundry. The PRR added them to their roster in 1929. A diagram of these tank cars is available on the PRR Railfan web site. I have not been able to find a prototype photo of the PRR TM8 car.