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).
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).