You took a very good example what can happen to an early and desirable German Zono model. My first picture shows the Concert-Zonophon No. 75 with 75 cm brass horn, glass plates and peculiar arm with upright support rod in a catalogue entry of September 1905.Steve wrote:The timing is prescient or somewhat fortuitous:
http://www.gramophones.uk.com/informati ... 0_hor.html
Note the identical winder and horn on this DRGM machine!

It was not at all uncommon that, after some years in use, front mount Zonos were converted in back mount machines to improve sound quality and operating comfort. Customers at the time didn't care much about brands and consistency.
The taste of the times changes. Nowadays front mount machines are much more in demand than converted specimen. This leads to the unavoidable: Historically evolved machines are again converted, as in this case. The traces of the back bracket of unknown maker are clearly visible. The dealer pointed this out, but it is of course far removed from the historically authentic condition.

If you discover an early Zonophon case in the wild, loose parts (crank, horn, reproducer) are nearly always missing. Consequently, certain parts (curved crank, brass horn, early type of reproducer) are very rare. When this machine was rebuilt, the dealer or collector used spare parts at hand. The straight crank is much too large for the graceful case. The top plate had to be trimmed to fit the crank. The result is an ugly and far-reaching interference.
Instead of an early reproducer a later model was installed which looks strangely out of place.

Nickel plated horns, manufactured from a few large German horn manufacturers in different sizes are indeed much more commonly found than brass horns. Again, I could live with the nickel plated exchange horn.
A serious drawback of this machine is the missing arm with upright support rod. An original spare part is near impossible to get. Hence, a standard arm was used.

In summary, catalogues can occasionally lead you on the wrong track, but if you neglect this original source it would possibly never occur to you that this is no special German variety, but the travesty of a rare machine. The dealer seems to be aware of this, hence the low asking price compared to an untouched Concert-Zonophon No. 75.