The passcode that comes with the Raven can only be used 1 time, so if the original owner has registered the Raven using this passcode it cannot be registered again.
When purchasing a used Raven, the previous owner will have to contact Slate MT in order to transfer the Registration to the new users account.
If the buyer of the used Raven is going to be on a different DAW, this extra DAW can be purchased in the Slate account in the Raven tab once the registration has been transferred. However, this additional passcode is only offered at the $99 discounted price if its the 2nd Raven license you are purchasing, as the 1st license is included in the purchase price when buying a new Raven.
In order to get the $99 additional passcode, the original owner will have to transfer the iLok to the new user's iLok account and pay the $25 transfer fee. Even if the new user isn't going to be using the transferred DAW license it is important to have the license in order to buy additional licenses. These licenses will be important if the Raven is ever sold or used in a different studio as the more DAWs on your iLok the more the Raven is worth.