The shape of the blade and the nakago would indicate a blade made in the 17th-18th century. It is most likely 17th c. as sword making fell off in most of the 18th c. due to lack of demand for new blades as there was no war. The blade is likely par of a multiple order for blades from a daimyo for his samurai. That would indicate the lack of a signature. More exact information can only be determined by a hands on examination by an individual of very advanced knowledge.