Wow! Harry, good call!!
While of course this is not a 'shashka' per se', It certainly is an anomaly which is likely in the spectrum of variants as Ottoman forces were being 'westernized' as well as the possibility of this being aligned with the Caucasian and Balkan forces of the Ottomans.
The clefted pommel with the characteristic shashka profile as well as the blade, which seems compellingly like East European (often Hungarian) forms which also were often seen on shashkas, suggest possible association in Janissary units (?) or those using Caucasian forces.
As Teodor well notes, the guard, though incongruent, looks like an Ottoman military type.
There have been numbers of these unusual hybrids coming from Ottoman ranks, and one other type I think of is the sabre which for all intents and purposes like a kilij or pala with a stirrup type knuckleguard, and these were 19th century as well.
Excellent example !!!
