I just did some quick Google searches, and nickel silver appears to be some type of silver plate. Coin silver flatware (from the 1800s here in US) is different. Coin silver flatware is 90% silver and was made by melting the 90% silver coins that were circulating back then. I have a little bit of old "coin silver" flatware from the mid 1800s I bought for melt that was to be sent to the refiner. Kind of cool though it doesn't say "silver" on it anywhere, just the silver smith's name, in my case H. HUDSON, who was a US silver smith in KY from 1841 to 1855 or so.
Just my 2 cents.
Jim