You don't need 'proof' that the 15/40 version isn't classic. The 15/40 ratio on a weapon for a dual-wield class is proof enough all on its own. That's far superior to other weapons you could obtain at that level range (which are typically in the 3-4 or so ratio range, see Brazen Brazz kilij, Crystalline Blade, Runed Falchion, etc) and is actually a better ratio than an SSOY. In fact it's nearly equivalent to some planar weapons such as the 15/38 Spirioc Wingblade in Sky (no wonder your bard likes having it, heh).
Additionally, browsing archived versions of EQ equipment sites show absolutely no trace of that weapon prior to Luclin. It was pretty common knowledge that the second step of the quest was broken for a very, very long time. Even the first step for the 6/28 sword periodically broke.
Screenshots of the initial Gnoll Slayer show it as non-magical as late as 2001, here's a 2001-era link:
http://web.archive.org/web/200108231....html?item=233
Some folks claimed to have found the second version prior to Luclin, but such claims were invariably rumors without evidence.
Danth