Silver bowl that will not polish

I have a newport silverplate bowl 1877 with green enamel inside bowl . It is well tarnished but I spent 20 min in just one area and nothing! It does not appear to be lacquered. I am using wrights cream polish. Any suggestions?

 

40 minutes........

 

We need to see it, but I'm leaning toward the kind of finish that cannot be removed. I tried once to clean a coffee pot of my Mom's and ran into the same issue. A so-called non-tarnish surface that does tarnish after all but can't be cleaned.

 

Are you sure it's regular silverplate - green enamel inside suggests it may be pewter (which won't polish).

 

Maybe Britannia ware, Pewter alloy?? It'll clean up a bit, but doesn't really polish....

 

Unlikely to be pewter with a Newport Silverplate marking and "Britannia" is not a designation that is used in the US.

 

It's possible someone already polished this to death - if it's down to the "white metal" that's all she wrote.

 

I am afraid Bakersgma's reply is what I suspect. It says silverplate and there are some on the internet. Non tarnish and non polish! It is in excellent shape so sad to just have to junk it. I even tried the katsup. Since it is already junk maybe I will try the dreaded Tarnex. Thanks everyone.

If it had shown even a little improvement I would have done 40 min! But one little spot for 20 min and nothing.
.

 

I have a beautiful aesthetic period pitcher in the basement like this, won't polish. I just assumed that as @evelyb30 said, someone had polished it to death. It has spots that are brighter than others but overall looks in poor condition. I didn't think they had those coatings back then.