Reinhold Manteuffel & Co. Information.
This company was active before WW2, when it manufactured a range of airguns in Zella Mehlis, and after the War in what became East Germany.
Here is the front of a Manteuffel catalogue from 1928.
The company also made bugelspanner-type rifles. Here is its playful logo, MAN plus teuf(f)el (devil).
The writer Ernst G. Dieter, in <i>Air rifles and air pistols after 1945 in Suhl and Zella-Mehlis</i>, said the numbers 1 and 2 and letter S inside triangles were East German quality marks.
Two of the following rifles display this quality mark, although it has perhaps been applied retrospectively to pre-WW2 rifles. The first rifle does not have it, but seems to resemble the other two in some respects.
Note that the rifles below are suspected, but not verfied, examples from this manufacturer.
With thanks to Keld for these pics, to Eberhard, and to Frank for some of the above research.
Rifle 1
Rifle 2
Rifle 3