If this card is Normal or Special Summoned: You can add 1 "Ancient Gear" card from your Deck to your hand, except "Ancient Gear Wyvern", also you cannot Set cards for the rest of this turn. You can only use this effect of "Ancient Gear Wyvern" once per turn. If this card attacks, monsters in your opponent's possession cannot activate their effects until the end of the Damage Step.
...What else could "for the rest of this turn" possibly mean?
The point is mostly to stop you being able to use it with Ancient Gear Drill, turning it into a generic search-any-Spell card. (Though it has the unfortunate downside of making the already unfortunate Ancient Gear Reborn worse.)