As you well note Guy, countless variations and hybrids found out there are some times close from astonishing or, if one prefers, do look unreal.
I would humbly advance that some particulars in this example look made by a handyman, as opposed to a regular regular smith; that back spike, together with fixation to the blade, sure look unorthodox, so to say. On the other hand, it would be a good sign if the inscriptions run symmetrically along the place where they are engraved... if i make myself understood.
I bet you are aware of HAFTED WEAPONS IN MEDIEVAL AND RENAISSANCE EUROPE by John Walman. Could your example belong in the same typology of the attached ?
... Notwithstanding the posture of your piece's main blade indeed reminds the shape of a bardiche
Please take all my words with lots of salt; no expertise here
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