This appears to be an R 4010. From the Schiffmann Sammerkatalog: "with eccentric - 36 (cm,) black hand painting reversal, 2 fixed double-acting cylinders act on the rear axle, drive rods, gallery rods, (1929 - 1932.)"
Great find, an early Marklin American market live steamer. Here's a page from the Marklin 1930 catalog showing the R 4010.
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