(under the class definition) Apparatus comprising at least two impellers* or working members* which differ significantly in structure other than by size or orientation.
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120+, for a plurality of impellers mounted for relative motion or on independent supports, which impellers may differ significantly in structure (i.e., not mere size or orientation relative to a fixed point).
203, for working members which are unsymmetrical relative to a plane, i.e., they differ from each other in orientation or size.
