Far from a complete reference, but there is a small entry on the Charpentiers d'Europe et d'ailleurs site put in place by the Ministère de la Culture et Communication in France.
English version:
http://www.en.charpentiers.culture.fr/node/628French version:
http://www.charpentiers.culture.fr/lesoutils/diversiteregionale/diversitedeshachesequarrir/piochond%E2%80%99alsacehautrhin
The English version describes it as a single bevel, while the French version claims double bevel. I think they're referring to cutting edges, but perhaps you can shed some light on it with your tool.
The mortising end of the full Bisaïgue (Can't remember it's name in German off-hand. I did find it before.) looks similar to the mortising end of the Kreuzaxt. The difference is that the Kreuzaxt is used in a striking motion, while the bisaigue is pushed from the shoulder.
