Translation of characters on antique metal During my last visit in Shanghai I bought this old pice of metal, it might be silver. What are the characters on it? I am having trouble reading them. Also, what do they mean?
It looks identical to this (you are looking at it up side down).

https://goods.ruten.com.tw/item/show?21737114069034

It says 大明宣德年裸銀寶至上.

I don't know how exactly to translate this (someone can help me out here), but if I have to...

大明 refers to the Ming dynasty.

宣德年 means the era of Xuande, about AD 1425 - 1435.

裸銀寶 means raw silver sycee.

至上 PERHAPS means your highness (this is probably a wild guess).