I think it is not old enough to be ko shoami but it could be shoami. I think all the damage gives the sense of the piece being older but I don't think it is pre edo. As for the theme it is a torii, cedar trees, and a string. It is described in Japanese at that website but using yahoo bablefish to translate doesn't make complete sense. If I understand the translation it almost sounds like marrriage and the wife keeping tabs on the husband via the string. That sounds about right. Take all of this with a grain of salt, I'm still learning but maybe it will get the discussion going.
http://www.finesword.co.jp/sale/kodougu ... 7/1195.htm