One of the most important figures in post-war American OO gauge was Frederick E. Schorr of Hazelton, PA. A very active OO modeler, to keep OO supplied with new equipment he imported brass models from Japan beginning in 1955 (more here), produced one new model domestically, and bought and sold a great deal of used OO. His son Ed was also active in OO and assisted with the business.
The only model in the line not imported from Japan was the F-3, available as an A or B unit. This model is normally seen in sand cast bronze although I understand that it was also produced in aluminum. This model was later also produced by Ultimate Screw Machine. This particular model in the photo has had Kemtron sideframes substituted for the original Schorr sideframes and weighs more than two and a half pounds!
The locomotives imported from Japan include a Ma and Pa 2-8-0, a DL&W camelback 4-6-0, and an Alco RS-2 diesel. All are highly desirable models.
Another unique model was the RDC in three versions. This contemporary self propelled passenger car was imported as an RDC-1 (coach), RDC-2 (coach-baggage), and an RDC-3 (coach-baggage-mail). The model in the photo is an unpowered RDC-1.
Finally we get to their great freight cars which are among the best looking ever produced in OO. These models included a covered cement hopper (two bay), a gondola, twin and triple hopper cars (ribbed side) and a CV wood caboose. These rode on probably the best trucks ever manufactured in OO, which were either spring arch bar trucks or sprung Bettendorf trucks.
UPDATE: More on Schorr here, with links to photos and info on most of the models in his fairly extensive OO line.