Yesterday I got these 3/16 Marx car frames for parts, mainly the type B trucks with plastic scissors couplers. I'm interested to know what cars used these frames. The shorter 6-inch frame has a center-pivot, presumably for a crane or searchlight. The longer 8-inch frame has a special attachment on one truck for a center-rail pickup (parts missing) and tab slots in the center part of the frame for a housing of some kind, also an insulated solder terminal for whatever was featured on this car.
Is there a good online reference with photos for Marx 3/16 trains?