Do I have to show my hand?
Trick won in dummy. Declarer says "dummy is good". It isn't, opposition object.
Opposition can take two tricks if they can see declarer's hand, but only one (unless they're very lucky) if they can't.
Declarer doesn't want to face his hand because he's giving them "an unfair advantage" if he does. According to 68C ("The player making the claim or concession faces his hand.") he has to, but on the principle that the laws seek to allow play to continue as normally as possible, is there any way he can avoid doing so?
This is a thought experiment (based on a similar situation), so yes I know Declarer is already giving info away by not wanting to face his hand, but please ignore that.