This may be a little bit off topic (or mabey not), but I’m sure somebody here will know…just by looking at a metal (flute, whistle, jelewry, etc) can you tell if it’s nickel or silver?
Just give it to your wife as a gift. You’ll find out fairly quickly.
Now that was a chauvanistic thing to say, Mr. Sharp. shame on you.
Give me a wife. 
Hmmmmm. Well, with a whistle, if is isn’t a Copeland, it probably isn’t silver. Even if it is, it probably isn’t silver.
With jewelry, if ist isn’t marked as silver, it almost certainly isn’t. Sterling silver can carrry a number of marks; 925, 812 “Sterling” being the most common. Pure silver is soft and tarnishes readily. Rub vigorously on the black stuff with a soft cloth. If it gets shiny, it’s likely silver or silver plate. Still, if the matter is important to you, the rule of thumb is “If it don’t say SILVER it probably isn’t.”
With flutes, I haven’t a clue in the world.
Quote @ Chuck_Clark
With flutes, I haven’t a clue in the world.
And of course, it’s a flute in question. LOL.
I bought it as ‘either silver or nickel plated’. It’s not really a pressing issue, I’ve just wondered from time to time what it actually was. I have a (finger) ring made of the same metal, too.
I thought there’d be an easy visual way to tell the two apart that I didn’t know to look for.
When I was in high school, I thought the nickel plated trumpets looked a little “darker” than the silver plated ones, it seemed relatively easy to tell the difference when comparing the two metals side by side. I don’t know of any way to test for sure though, HELP, is there a metalurgist in the house?
They make solutions that intentionally tarnish silver to create an antique-looking patina. I believe trying that would be a way to tell, if there’s no lacquer on the metal. Then you would polish off the patina with silver polish. I don’t think nickel would act the same way.
There are jewellers who post here. Jessie? Serp?
Best wishes,
Jerry
Your new avatar softens my usual grumpiness, so I’ll try and help 
Pure nickel plating has a warmer tone than sterling silver, but this works only with older platings. If new, or spit-shined, modern plated flutes can’t be told from their looks alone. So…
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The stamps vary widely from country to country, and you have to be a jeweller to tell if a genuine sterling-silver mark was punched in… I have a whole set of spoons and fork made of a high-copper content white alloy (sort of sterling-silver) with each a full collection of authentic-looking stamps punched in. This was a pre-war hoax, though one of the engravings now tells the tale : “Nevada silver”. I even suspect the alloy contains some lead… for weight.
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If you have a nickel plating, the base stock will likely be brass, or copper, or even steel. Either will be lighter than silver by ca. 20% to 25%. Silver is almost as heavy as lead. A silver flute will be noticeably heavier than its plated look-alike by the same maker. You can feel it with bare hands, no scales needed.
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Now, if you can borrow the instrument for an hour… Do it, and go for the full works!
Immerse some part of the instrument (like the head) in water, preferably in a vertical bottle, not a pan. Fill it to the brim. Carefully remove the whistle part. Put your bottle on a scale, weigh it for W1.
Carefully fill again the bottle to the brim, weigh it for W2.
Now weigh the whistle part you used (W3).
If the weight of the metal part divided by the weight of the water it displaces [i.e. W3 / (W2-W1)] is 10 or slightly more, it’s silver.
If it’s around 8.5, it’s probably brass or some other copper-based alloy.
what’s the deal with flutes that are marked “coin silver”?
[what’s the deal with flutes that are marked “coin silver”?]
In the US, sterling silver is nominally 925/1000 pure silver while coin silver is nominally 900/1000 pure — sterling silver is kind of soft to be used for anything subject to wear — coin silver is considerably harder, due to the alloying metals, although it will still wear, albeit more slowly — see an old, circulated US (real) silver coin. Note that the British did use sterling for coins — they also * severely * discouraged the clipping or filing of coins. If something is stamped “coin” or “sterling” silver, it should be solid, not plated.