lets say for example if there were only 2 million notes made and they were signed jenkins dodge.... the next prefix out is XYZ(example) and it is signed out Carney/Jenkins, the BTR would be a changeover. This would possibly warrant a highter premium.
On the other hand, if BTS came out, your BTR would be just prefix notes and not gain that much of a premium.
Cheers
Polarbear