Japanese Artwork

I inherited four pieces of Japanese art, they come with certificates of authentication. I have tried to part with them in the last six months, but have no clue as to the value of each. I put them on eBay for a while, but no takers. I tried to research them by reaching out to the Smithsonian, that got me nowhere fast. Does anyone have any familiarity to these, the are comprised of: silver, gold, and burnished copper.