Singapore 10 dollars 1977

I recently acquired this coin. Its design and size is exactly the same as the silver 10 dollars 1977 listed in numista. But it is not silver and it seems to have been mounted to something. It is not magnetic.
Does anyone know if this is a genuine coin or a replica?

And how do you know that it is not silver? Did you do some tests? I am asking because for me the tarnishing (though it's not easy to judge by your picture due to the brownish hue of it) looks like silver one and usually people make such kind of pendants out of silver coins. If it is true, the weight should be about 0.1 g more (my guesstimate for the weight of the bail and a drop of solder).
By the way, Krause doesn't list nickel version of this coin (it may not exist). The very similar 10 dollar issued next year (1978, Communications Satellites) has both silver and nickel version, and the nickel version is 3.1 gram lighter (28 g instead of 31.1 g) - so, if your coins is nickel, it should weight the same 28 g, not 31g.