Can not find much information ofn this maker, there are a couple of pinfire revolvers for sale/auction if you look on Google under the name and a pinfire combination gun referenced at http://forums.nitroexpress.com/showflat ... n=0&page=2
You probably already know that Herzberg is a small city in the Brandenburg region of Germany and B. Ebbeke (I assume) was a gunmaker of that area.
The gun uses the Lefaucheux 'bolting' mechanism which was probably the earliest drop-down action type. The action, however, has me beat. Are the firing pins internal and the external hammers purely a cocking device ?.
The only set-up I can find that looks kind of similiar was French Patent #9058 awarded to Louis Julien Gastinne in 1853.
Charles Lancaster, of London, England, had some involvement in the further development of this patent and by 1859 was producing similiar guns.
Thats all I can think of at the moment and my apologies if it's of little help.