Hi Micky,
According to The Encyclopedia of Spring Air Pistols (John Griffiths), there was also a small frame version of the Hubertus marked "Jungson" with a Ser No much higher than other, small frame pistols. A likely prototype extended variant which appears to be a genuine factory modification is also pictured and described as a possible attempt to produce a combination pistol capable of firing small cartridges as well as pellets.
Regards
Brian