Polish sabre?

[Jim McDougall]

I very much agree, this is an outstanding example of these very well known sabres most associated with the storied "Wings Hussars of Poland". As Oliver notes, these swords were typically Hungarian as well as Polish, however they were of course equally diffused into many contiguous regions including those considered Russian.
The term Russia was not commonly applied to refer to any particular of these regions as a 'state' until the 17th century.
It was also a common convention to refer regionally to such areas by the name or term for a defined large or important city , Q.E.D. so Moscva would have referred broadly to Russian regions.

The latten filled inscription on the blade back and the mark with initials suggest plausibly Solingen as its place of manufacture as this was well instituted in the character of, though not entirely confined to their blades.
The mark of the unicorn was used by both Johann Henckels (c.1600) and Clemens Horn (1586-1631) but these were typically heads only. The full body may signify use alluding to the quality of those blades and used by another in later date in accord with the inscription.
The use of Latin in inscriptions was common in those times as it was the lingua francia and transcended linguistic barriers.

It would seem that 'commemorative' dates were often applied to blades in these areas, and that this date applies to this significant treaty suggests obviously the diplomatic potential for this sword.