Cool coins, I had no idea so many different versions existed...
"Only two out of all silver 0.5 BTC coins are known to have been opened."
I lol'ed at that as I can see all the hardcore collectors out there screaming "NEVER OPEN A LIMITED EDITION ITEM" at their computer screens.
Yes the value of the coin dies when you pull the holo off the back! Is a bit of a no no among the collectors!
I recently was given a limited edition Star Wars drone as a gift... The caveat though was I would only be given it if I actually opened it... Needless to say it hurt like hell to break that wax seal and open that sucker up. I could hear the hardcore Star Wars collectors dying a little inside as I did it (LOL).