a) GBC has value because it is backed by X amount of Gold.
b) If the price drops too low, you will sell some of the Gold to prop the price up.
c) Now GBC is only backed by Y < X amount of Gold.
d) So the price goes down.
e) Goto b, until you run out of Gold.
You cannot maintain a currency peg against a determined attack.
George Soros proved that, if it needed proving.
Your argument is false.
The moment we sell 1 GBC to you, we back it by 1/10th of an ounce of gold. This is for your security.
The moment we buy back 1 Gold Backed Coin from you, you get your money. And after we bought back this 1 GBC and it's in our possession again, then this 1 GBC does not need to be backed anymore. Got it? And: All GBC out on the market will still be backed by 1/10 of an ounce of gold each - and that doesn't change.
Well, can you explain what you want to say with your example of a Soros-like attack? There are some missing links in the art of logic you apply, so I can only recognize a hollow allegation driven by undefined fear...