How do you see which character has unlocked a certain item, title or mount?

[fearfart]

Hey,
As many of you, over the years I've built up an enormous collection of alts, vanity items and mounts on my WoW account.
I'm looking to cut back on the amount a bit, keeping only my main and a few core alts to play and enjoy the game on. However, with the account wide systems that've been added over the years, I find it hard to see which character owns what.
How do I see which mount or which title belongs to a certain character, so that I can tell my buyer about everything he'll be recieving by buying my alt?

Is there no other way than transferring the characters out by trial and error?

Thanks in advance guys!

[jujuu]

Achievements will show which character earned said achievement if you mouse over the shield on the right side that shows how many points the achievement is worth. Other than that I don't think there is a reliable way to see who earned what.