This is a really wonderful Soshu ko-wakizashi with a hitatsura hamon that is full of activity. I will say at the outset that the sword has a mei of Muramasa and a sayagaki from Sato Kanzan which supports that mei, however I am doubtful. Looking at just the blade itself, I believe it to be Muromachi Soshu, such as Hiromasa. The hamon is full of bright, uniform ko-nie with profuse hataraki. The jihada is a large patterned itame. This is a wide and healthy hirazukuri wakizashi. Please see below for dimensions:
This blade is in shirasaya with a very well made gold foil habaki with a solid silver base.
$6,600 (plus shipping and PayPal)