Question for GC from Diablo

Hello ! I’m a new player and I want to ask a question. I found a Grand Charm from Diablo. My question is how can I prove that it is from and what price can I charge for it.

You can cube it together with 3 perfect gems, till you get the “of Vita” affix with 41 or more to life.
I suspect it’s not this much worth, even with 41+ life proof, because of the terror zones there are much more monster except Diablo, Nilathak and Baal, who can drop this charms.

With online vendors gone rampant, you can buy BER’s for just 16 cents. Nothing is worth much any more. I would recommend getting an account on traderies where you can check any item to see what it is worth trading.