I also think that if a letter is on file showing that you have enquired about a specific gun, and at a later date it was involved in a crime, you can rest assured you would get the third degree over your ownership of it. The fact that you never bought it or sold it three owners removed would be unimportant
I'm very sorry to contradict, but I happen to be working in a profession where I have to deal with legalities (and charges being laid against non-law abiding citizens) on a constant basis... and I can tell you here and now that, with the way the letters are set up and the way we are free to sell our antiques to others (nationally or even abroad), there is no way in hell you can get into trouble over an antique gun you received a letter for that was later involved in a crime. Yes, there is a link to you, but it would take a hell of a lot more than that to put you in the hot seat. You'd probably just get a call from the SD (sergeant detective) leading the investigation and he'd ask you a few basic questions about the whereabouts of the antique gun you once requested a letter for. The only way it could turn bad for you is if there is other evidence to link you to the actual crime they're investigating (ie. eye witnesses that recognized you, camera footage with your face in it, etc)... but then it would be deserved, wouldn't it?
NOW... having said that, I have never heard of a case where an antique would've been used in the commission of a crime. People who do commit crimes with firearms usually get their guns from other sources, smuggled in automatics being their all time favorites (you rarely even see modern revolvers - too bulky and not "gangsta" enough for today's youth). Even if they could get their hands on an antique, why would they? It costs more than a street gun, is over 100 years old, plus you can't find (or steal) proper ammo for it anywhere these days (and those bohonks are way too dumb and too high to learn how to reload anyway).
Bottom line is, further legislature in this matter is both pointless and useless.. antique guns are solely for the most dedicated and most professional class of firearm collectors (because of their prices and the necessity to create your own custom ammo for them, if you intend to shoot them on occasion). So, as long as some dimwitted gramps doesn't get the bright idea of going postal with a flintlock, I'm pretty sure we won't have any issues.
P.S. In the next few days, I'll be calling the RCMP in regards to two more letters for antiques I will be most likely selling in the near future... this is how concerned I am about getting in trouble over it one day or being "linked" to something...