Good point Mooncoon. I neglected to remind of the obvious flaw to the CBSA's regs: U.S. Antique definitions and Canadian ones aren't the same. A fair number of firearms qualify as Antique in the U.S. that don't here.
BrotherR: you might want to make sure that the U.S. dealer writing the letter makes it clear that he is certifying the authenticity in accordance with Canadian Laws/Regs.
The following is taken from "Regulations Prescribing Antique Firearms (SOR/98-464)", which can be found at:
"http://laws.justice.gc.ca/en/showdoc/cr/SOR-98-464/bo-ga:s_1::bo-ga:s_2?page=2" (Okay, so I don't know how to add hot-links).
It might not hurt to include this description in his letter, or at least refer to it. I've brought several Antiques over into Canada in the past, and it always seemed to me that as soon as CBSA staff saw that I had done my homework & was on top of the laws/regs, they were really cool to deal with. I've spent far longer in lines waiting to be served (and back at the vehicle chatting with two young officers who really liked my Sharps carbine) than ever getting 'hassled' in any way.
"HANDGUNS
6. A handgun manufactured before 1898 that is capable of discharging only rim-fire cartridges, other than 22 Calibre Short, 22 Calibre Long or 22 Calibre Long Rifle cartridges.
7. A handgun manufactured before 1898 that is capable of discharging centre-fire cartridges, other than a handgun designed or adapted to discharge 32 Short Colt, 32 Long Colt, 32 Smith and Wesson, 32 Smith and Wesson Long, 32-20 Winchester, 38 Smith and Wesson, 38 Short Colt, 38 Long Colt, 38-40 Winchester, 44-40 Winchester, or 45 Colt cartridges."