Bernard,
In regard to the tsuba in the first image of this post, I am would have to politely disagree with those who are calling this anything other than true inlay. If one looks carefully at the image you can see missing pieces of the inlay. Also, the galvanic reaction between iron and a more noble metal such as brass, will cause the shadow of rust on to the brass over time as the iron is sacrificed. Also, the method of mercury gilding is only applicable to soft metals, not iron.
Thank you for showing,
Marcus