Adler 'Niederrad' no. 9

This bicycle is a German Adler, serial nr 14469,  from Frankfurt, it was built between 1891 and 1894.
It is a unique crossover between the original CMC Swift and the later model CMC Swift. It has got the curved lines of the original, but the two 10 mm. tubes to replace a saddle tube that we see on the later CMC Swift.

The early Swift-model was built in license by some other manufacturers, like Adler, Opel and Mégret. Adler was the only one who built this crossover: a lighter version of the old and heavy CMC Swift, yet reinforced bij the two thin tubes of the later Swift. You will find this bike in the 1893 Adler catalogue, although some details are different. 
Some details, like the 'flat' bracket and the transverse lug to attach the saddle, are exactly the same as an earlier Adler model in the Bad Bruckenau bicycle museum. 

This Adler is really a quality machine, with an interesting steering lock which resembles the Singer patent of 1891, see illustration.
It's not sure if hubs, rims and spokes are original. Front and rear wheel may have been replaced. 

From the Adler 1893 catalogue,
thanks to the Velorama museum!