Experimental Austro - Hungarian M 1888 bayonet (No ref.)

Unknown rifle. ( Mannlicher M 1888 ?) No serial number. Excellent++ bright finished plain blade with no false edge. No makers name nor markings to the bayonet. Very well made hilt with wooden scales fixed to the blade by screw bolts. No oil hole. Excellent blued square crossguard with a backwards spoon shaped swept quillon and a muzzle ring MRD:16,5 mm. Blued pommel with a small working catch and T-slot. The pommel is unusual made of two parts attached to the blade tang.
Excellent+ blackened rather flat steel scabbard with an oversized throat and a small German style frog stud. No dents to the scabbard.
Total length: 36,7 cm, Blade length: 24,5 cm. Hilt length. 11,2 cm. Width at the ricasso: 2,5 cm.

Very well made, beautiful bayonet.  The country of origin is speculative. It could be another country. But the crossguard, the MRD and the other dimentions are equal to the Austro-Hungarian M 1888 and M1888/90 Ersatz bayonet (ABCN335 1-2).

No doubt a extremely rare bayonet, but what is it?.  If you know what bayonet this is, please let us know.