FWIW, the holder of a C&R license does not have to send in his record book if he chooses not to renew the license. For a dealer or manufacturer, the "bound book" is a business record and must be sent to BATFE if the business license expires. But a collector is not in business and a C&R license is not a business license. Thus, his book is not a business record, and does not need to be sent in on the expiration of the license.
Jim