We do not live in a world that values "doing the right thing" only a world where we look to minimize our own exposure.
The Antiquorum lawyers do not care about you, the Consignor, or the watch. Their sole concern is the welfare of their employer. I am sure they believe the watch is stolen and you are the rightful owner. But what is the path of least exposure for them? To wash their hands of the affair and return the watch to whence it came. To actually do the right thing and help you obtain your timepiece would expose them on two fronts: (1) the very small chance (to them) that you are not the rightful owner and the consignor can bring legal action on why his watch was removed from him; but more importantly, (2) to do so would be to admit that they sometimes receive stolen goods. This is an admission I am sure their lawyers would never allow them to make.
So you are the victim again, first of a robbery and now of a "cover my own ass" mentality that is every bit as damaging.
I feel for you, my friend, and I wish you every success should you pursue this through legal action.
NickO