A couple of notes about 'TN'
… It's all beginning to make sense now.
This page … http://www.idref.fr/151499225
gives some details of the Technicum neuchâtelois (Le Locle – La Chaux-de-Fonds)
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The rating plate on the pantograph motor [in the base of the machine] identifies the manufacturer as the 'School of Electrical Engineering' at said Technical College.

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I therefore think it reasonable to assume that the pantograph machine was built by the College, as a commercial venture … Rather like some of the spin-off business conducted by Cambridge.
MichaelG.