With thanks to John Z for the first pic of the common earlier model, which had a zinc alloy barrel surround and frame and brown wood grips. (source: John Griffiths, <i>Encyclopedia of Spring Air Pistols</i>).
These pics are of the rare later version, which had an anodised alloy barrel surround and frame, and bakelite grips. (source: John Griffiths, <i>Encyclopedia of Spring Air Pistols</i>).
Haenel mod 26 (painted black)
With thanks to Wiley for these pics.
He says: "The pistol I have only has the Brit Pat number on the top of the
receiver. On the whole it looks a great deal like the pistol in the
brochure written in German. The example I have is rifled (a Google search of the words in the catalog indicates it was
available either rifled or smooth bore). The frame and barrel on my
example is made of aluminum rather than zinc alloy (as noted in the
photos). The front sight is simply held by dovetail no locking or
adjustment screw. Grips are wood like the example you have in your
gallery. It is .177 caliber.
The one I have was painted, perhaps repainted in its past. I was told my
father got it new as a boy back in the 1930s. No box or other brochure
Other than the spring holding the cocking arm in the up position being
broken (same one as shown being replaced in your photos), the pistol works..
I have always found it interesting that it would appear that the notch cut in the rear sight was done after the pistol was assembled and shot. It would seem that since there is no windage adjustment that they somehow fixed in position the pistol; then shot to see where it grouped and cut the notch to align with that grouping. To me this would cause all sorts of issues as the actual path of the pellet would create one line which would intersect the line created by the front and rear sight. This would be fine at some "set distance", any target further way the two lines would diverge as they would on any target that was closer.
The idea that they somehow shot the pistol. Then removed it from that "fixed" position, cocked and reloaded and returned to that same position enough times to get a grouping seems far fetched. But I can see no other reason for the notch to be cut off center."