Duo Model-VI Repeater - Haenel.
This rifle seems to bear an uncanny resemblance to a Haenel repeater, but has the markings of the Czech Duo company.
The jury seems to be out as to whether it was made by Haenel and exported, or was a close copy of their design? German collector Eberhard points out that before WW1 Czechoslovakia was integrated into Austro-Hungary, that many German-speaking people lived in the border areas between the two countries, and that many guns, including airguns, were made there. It may be that Haenel looked to Czechoslovakia as an export market, facing stiff competition within Germany from Diana and Oskar Will, and rebranded the guns to meet Czech sensitivities over buying German imports? Or maybe they were made under licence (or otherwise) in Czechoslovakia?
With thanks to Vaclav for this first set of pics.
This rifle was advertised on eGun.de recently:
This is possibly the same rifle as the above, or a third example, advertised for sale on eGun.de in December 2019:
This close up of the Duo logo appeared in another eGun ad for a rifle looking just like a Haenel mod II.