Adler 'Niederrad' no. 13, c. 1893

Okay - it has some bad replacement parts and is not complete. But this Adler from Frankfurt (Germany)  shows its quality and some nice Adler-details.  Serial number is 18672 and I guess it was built in 1893-94. 

Let's start with the good things: this Adler no. 13 has a very sophisticated frame. Adler really paid attention to details. It still has the original saddle, rear mudguards and front wheel - meant to take a pneumatic tire. Look at the nice steering lock and the original lamp post. 
The no. 13 (introduced in 1893, see catalogue scan) had an interesting front wheel brake, acting at the hub. Must have been something like on this Columbia. It's a shame it's missing on this bicycle, but you can still see where it has been attached at the front fork and front hub,. 
Rear hub has been changed, I have my doubts about the front chain ring (but I am not sure) and the handlebars are a bad copy.

The owner will find some difficulties in restoring this bicycle: especially the front brake. When there is no other original left, how to make a copy?