Thank you for making your question to JustAnswer. My name is*****'m an Antiques Expert and I will try to help you with your particular inquiry. Please, don't hesitate to contact me any time or to make follow up questions if needed.
You have a silver plate manufacturer by SHEFFIELD SILVER COMPANY/ THE SHEFFIELD SILVER COMPANY. The number 1525 is the specific pattern number used. The NS (prima nysilver) is generic Swedish stamp to indicate silverplated nickel silver,
Regarding the value of your item, I have just perform a market research of similar sold items as yours. I performed the research based upon the most recent finished auctions and private sells, so the value given is the real market value of your item. This is the only way to know the exact value of your unit.
The value will be in the range of 40-70$.
Please, use the stars to rate my answer or let me know if I can help you any further!