In speaking with old tme musicians I know, the Stroh is (apparently)  
a patented design, and others are not true to the Stroh design. A  
violin with a horn is not by definition a Stroh.

More detail I don't know, but anyone can make one if they hve the  
skills, but it won't be a Stroh.

<http://strohviolin.com/>
says:

Our interest in phonofiddles, violinophones or strohviolins dates  
back to the early 1990s when discovering one of these unique  
instruments in a Thai/Burmese bordertown.Further research revealed  
that we had rediscovered a replica of an instrument, widely used in  
the early 20th century's recording industry - a Strohviolin - named  
after its German inventor and instrument designer Johannes Matthias  
Augustus Stroh


Google can tell you more...
<http://en.wikipedia.org/wiki/Stroh_violin>
<L>
On Oct 15, 2009, at 10:44 AM, RA Friedman wrote:

> Instruments with the horn at about 9-10 o'clock were from the  
> acoustic age.
> This one that is for sale seems like an updated idea; not authentic.
> Correct?