I've acquired a few Marx tin-box cars, probably mostly 1950's. So far just one of my cars has plastic wheels, a Pennsy #738701 high-side gondola with sliding tab and slot couplers. I'm just curious when Marx started using plastic wheels. The plastic wheels are fixed on the axles, not independently rotating. Does this create more drag on curves, enough to notice?
One other piece of interesting trivia: apparently the sliding tab-and-slot couplers were supplied only with clockwork sets. Was this because the coupler slack-action made it easier for a clockwork motor to start a train?
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