'Versuchsmuster' ('experimental') direct pull 3mm air rifle

'Versuchsmuster' ('experimental') direct pull 3mm air rifle 

With thanks to Guido for these pics (and Thoralf for facilitating).

Guido says: "Manufacturer: unknown (could be the company Heym?)
Calibre: 3 mm, single loader
Repeat to load. The ring can be pulled to 'tension'
Stock with mother of pearl inlays"

Apparently this rifle fires 3mm balls with low power. It is a true air rifle, with a spring piston inside the 'bolt'. The compressed air travels down the long transfer port, along the probe, which advances the ball along the barrel when the bolt is closed, like the probe on the front end of the Haenel 100 ball repeater piston. 'Versuchsmuster' is German for 'experimental'...