This is an outstanding blade!!! and if memory serves it would seem to correspond to Altaic sabres of the period you suggest. The angled tang (which becomes consistant in some Tatar sabres and the 'Mingrelian' shashkas among others) is seen on these 'Altaic' examples. I think there are good drawings of these in David Nicolle's work on the Mongols. The remains of the 'tunkou' at the blade root also seem consistant with these.
What an incredible find, and as noted, how unfortunate that more exacting provenance was lost,
It seems the remains of swords of this form were discussed a number of times over many years on these forums...can anybody help with the references in Nicolle (I think it is "the Mongol Warlords" that the drawings are in). I think the heading for the discussions here were 'Siberian sabre' ?
Very much looking forward to input on this as it appears an extremely important blade, and fascinating as the long standing and ever developing debates and discussions on the sabre form evolve.
Thank you again for sharing this blade!!!
All the best,
Jim