Can you tell if someone Played Vanilla/Classic Warcraft from their Achievements

[Serissa]

If someone thinks they were godly in Vanilla... check for Atiesh

Indeed, and doesn't matter if Naxx'60 was available until pre-wotlk event... oh wait :P

[Naibil]

There's a FoS achievement for acquiring the tabard from the opening of the Dark Portal event. Wouldn't that be proof?

This is what I was thinking as well.

There's no FoS attached, but if you have "Contest Winner's Tabard" I'd say that would be another pretty darn good way of proving it.

[Sound911]

PvP Titles, you'd get one if you got like what 10 kills or something - Rank 1.

[Oneru]

I was thinking the Feat of Strength The Fifth Element, for obtaining the Eternal Quintessence which was required to douse runes in Molten Core and unlock Majordomo (http://www.wowhead.com/achievement=2496). Seems that was still obtainable in TBC though (and WotLK, but only if you already started the questchain earlier).

Guess the only in-game proof are indeed the achievements for old pvp titles then.

[jaymzkerten]

I was thinking the Feat of Strength The Fifth Element, for obtaining the Eternal Quintessence which was required to douse runes in Molten Core and unlock Majordomo (http://www.wowhead.com/achievement=2496). Seems that was still obtainable in TBC though (and WotLK, but only if you already started the questchain earlier).

Guess the only in-game proof are indeed the achievements for old pvp titles then.

I didn't start the quest chain for that until Wrath had already hit, it wasn't until sometime later in the expansion that they removed the start of the quest chain (same time they put in the FoS).