NSU 'Pfeil' safety bicycle c 1897

This is a wonderful original safety, made by the German firm NSU. Its even got its original mudguards and saddle. 
The wooden rims were modern in the late 1890's, and very lightweight.
The sloping top tube however must have been oldfashioned at the time this machine was built.
The year? The Neckarsulmer (NSU) 'zweirad'-museum where I saw it, thinks it was made in 1897. They call the model 'Pfeil', which means 'Arrow'. 
I suppose they will know. But '97 is very late for a bicycle with sloping top tube. Alas I do not have any NSU catalogues to check it.

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