Best way to avoid this type of assles, is to have the gun verified by CFR prior to buy. If it qualify as an Antique here in Canada, they will provide you a letter confirming its antique status , and all you have to do is send a copy of this letter for the seller to insert in the box with the revolver. Once it arrives in customs, they will see the letter and usually they dont ask furter questions. If they need to questions they have a phone number on the letter they can check with the Firearm analyst who confirmed the antique status and issued the letter.
Hope this helps.