Copper or Bronze Urn Vase

I'm not sure if this is bronze,or copper. Iv'e eliminated brass as it's developed some green patina and i'm under the impression that brass will only darken, not go green.
Please correct me if I'm wrong!
The urn is painted in a mottled marble style
The urn is 7" 18 cm high
3 1/4" about 10 cm across the top
It's not flimsy at all and weighs 1lb 4 oz
The bottom is stamped SS
I did extensive searched for the mark in just about every metal I could think of but nothing
Anyone recognize the stamp and could possibly give a age range on it
The bottom picture shows its true color
Many thanks to all here