|period||Late Muromachi (ca. 1550)|
Ko-Kinko is a general term for Muromachi period goldsmiths. Out of the Ko-Kinko group you get the Ko-Mino smiths with their particular styles and then the Ko-Goto smiths, starting with Yujo who become the illustrious Goto school.
This kogai was put into a koshirae for a Tokubetsu Juyo sword as a replacement when someone took out the original kozuka-kogai pair to box them and sell them for short term money. I think I found the original pair and have returned it to the Tokuju sword's koshirae which cost a lot to do but restores the intention of the koshirae.
I can send this one in and it will take some time, and then it will paper I am sure to Ko-Kinko, Ko-Mino or Ko-Goto, in decreasing chances. So far people seem to think Ko-Mino is the reasonable attribution, but to be safe I'm just saying Ko-Kinko.
This kind of Muromachi goldsmithing was worn and used extensively. The gold applied on top of the shakudo for highlights as a result is usually worn by finger touching. The effect is considered authentic and desirable and is not to be taken as damage or something in need of restoration.
In order to save myself some time, I will just pass this one along as-is and I will give a 100% money back guarantee if it fails to paper to one of the above three schools. There is no box, as mentioned above, this was a stopgap someone put in place on a koshirae when a gold Goto futakoromono was separated from the original daimyo koshirae.
Feel free to price shop and make an offer.