Thanks Jim. The cars are Bachmann "Old Timers" Passenger cars. The best place to find them is at train shows. I wouldn't pay more than 5$ a piece and I also recommend giving them a good inspection before purchasing. Out of the 7 I have, only 3 are consistent with proper detail. The other 4 have a range of issues like a clerestory which was too tall, a clerestory which is too short, bowed undercarriages and poor mold detail instead of nice crisp lines. Also, the trucks have an issue where the indention for the pointed axles are too large and wide, which often cause axles to drop right out of the truck, as well as ride awkwardly. (You can clearly see these discrepancies in this and this roster shot.) Actually, you might be better off getting the Athearn 50' Overton Passenger cars. They're slightly longer, but they're much much better quality.
