United Kingdom 1 pound - Silver Proof or Silver Piedfort ? [opgelost]

I have this coin, N#56275, and how to identify, is it Silver Proof or Silver Piedfort, coin is thick :

Here are photos :

And how to grade and valuate it ( how to be objective, not subjective ) ?

This should give you a clue.

Ok, thanks, I did not see weight at all.

I will check.

Just looking at your pictures, I would say you have a circulated nickel-brass pound coin. What makes you think it is made of silver?

Just by color, it is look like silverish……

It's not got a frosted obverse. It's a normal £1 coin from circulation. Even if it was Brilliant Uncirculated, it's long lost that quality 

Yes, it is normal nickel-brass pound coin, not silver, silver coins are more bright, and this is not.

Thank You all for help.