The description of the buff says "Knowledge gained from the Lexicon gives you a 25% bonus while wearing Dwarven armor and Blacksmithing increases 15% faster."

I noticed a rather large increase in my armor rating after receiving the buff, only, I'm not wearing any dwarven armor... currently my character is wearing:

Ebony Mail (daedric artifact)
Ebony Gauntlets/Boots
Mask of Clavicus Vile
Spellbreaker

As far as I know, none of this stuff is dwarven. I can see Spellbreaker's base tier being dwarven, but unequipping doesn't remove the bonus to the other armor. Anyone notice this? Any confirmation this is a bug?

Yeah, it's glitched, it doesn't do either of what it says. It seems to enhance the rating from any armor, and as far as smithing goes it appears to fortify it rather than speed it up.

Be glad, it turns a limited buff into a bonus for any armor and makes up for the useless second part. Btw does the 2nd part fortify past 100? so if you're at 100 skill when you get it, it'll act like your using a fortify smithing potion when improving an item? or does it not even function properly in that way?

Ancient Knowledge is bugged, exactly how UnclePain said... it may also be F'ing with other skills besides smithing. A number of us take pains to avoid getting the perk, or use the console to remove it after finishing the quest, because we still don't know exactly how much it messes up your game. There have been reports of odd stat glitches after getting the perk.

-Loth