It strikes me as a
yanmaodao or maybe a liuyedao (see link and attached example from mandarinmansion; 1st picture subscripted "A 17th century yànmáodāo", second "A 17th-century liuyedao" and 3rd "An 18th-century liuyedao") but I have never seen a confirmed Mongolian sword so I can't speak to the origin.