This information is being used from the Drow Wars campaign book series.
A signature weapon/armor is a magical item that can only be used by it’s proper owner. In anyone else’s hand it is only a +1 item. While the owner can change, this only happens when it has been given freely.
As the character levels so does the signature item. Only when your character levels can you change what bonuses your weapon has. Please refer to the follow table.
|Character Level||Max Enhancement Bonus||Total Item Bonus|
For example: Kengi has just reached level 4 and his weapon was a +1 flaming weapon previously. At level 4 the max enhancement bonus raises to +2 so if he decides he can change it to a +2 weapon, leave it as a +1 flaming or change it to a +1 weapon with any other +1 enchantment.