Is it Plate Silver?
I found the marks on line. It is Prill Silver Co. Although it doesn’t have the EP stamp it may still be Silver Plate. Also this does not appear it was made in Sheffield England even with the stamp. Can this be confirmed?
Yes this is electroplate as it does not bear any indication of silver fineness, which we would expect for either American or British silver.
What makes you think it was not made in Sheffield? Because Prill was an American company it does not necessarily follow that they made all goods with their name on in the US. This was almost certainly made by a Sheffield company for Prill.
I read that many companies had set up in the USA to make the products, out sourcing? I thought my researched shows Prill one of them.