No extant maker's markings. This specimen is not a complete dynamo, but rather a circular armature with three sample windings on the rim. Construction consists of individual laminated metal sheets clamped to form a single unit. A radial type commutator (catalog number 309338) is used with this machine. US Patent #228544, Dynamo electric machine, issued 8 June 1880 to Hiram S. Maxim. Patent Claim: An armature for a dynamo electric machine constructed in such a way that all parts are open to free circulation of air.
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