This wonderful original Adler safety is visible in the German bicycle museum in Bad Bruckenau. It's very original and both hubs have ADLER inscripted in the middle of the hub.
This model is still very close to the original CMC safety, of which it is a copy. I suppose this bicycle, with serial number 97XX on top of the handlebars, was built around 1890 - although it's still features in the 1893 catalogue as the basic model. In later years, Adler started to develop its own models.
Click picture to see more on my Flickr site. It also shows a picture of the Adler nr. 5 from the 1893 catalogue. It was the only model by then still having the old fashioned pivot head.