I will look into the Hermann Historica auction catalogs in the next day for more dreyse guns. this rifle here was sold in 2012

http://www.hermann-historica.de/db2_de/auktion-65.html

N. Dreyse in Sömmerda made in 1860/61. cal. 12,5 mm, serial number. 334. barrel 60,5 cm long and made for prussian navy officer as a gift.
what we see is a beautyfull stutzen not a double but only one rifled barrel made as a break action in the general lines of the dreyse double gun ZIMMER describe as the "old " modell. giving as a gift in the beginning of 1861 it was probably made in 1860. the dreyse hunting gun was developt by Franz Dreyse in 1856 so I would think its the hunting gun number 334 made since 1856 AND ALL dreyse hunting guns are in one group of serial numbers

also a very early double gun with the number 2488 for the 0,64" randschlusspatrone and without the hooks on the action.

sold by HH in 2012 http://www.hermann-historica.de/db2_de/auktion-64.html

there was the 0,59", the 0,64", the 0,70" and the 0,74" and we can say that this is more or less a 28, 24, 20 and 16ga. and so we can also say that at least with gun number 2488 Dreyse make the gun for the randschlusspatrone. when we see that hunting gun number 334 was made in 1860 this are more or less 100 hunting guns a year and when thinking this was common Dreyse was close to number 2000 when the french - german war came in 1870. the dreyse factory was very busy to make military rifles in this decade so hunting guns were secondary. sometimes between 1969 and 1871 there must have been the change from the old to new model.
so whats now with the gun number 7506

Zimmer write in his book 1876 that Dreyse was still making the old model on special order. ok, its not realy the old model because its not the break action anymore but it looks like make for a paper cartridge. so this was maybe one of the special order guns.