AAVF.10 switched to a SHA-512 hash. Passwords are 9 hex digits.
The B10B has an autogenerated supervisor password (hashed from the serial number). Earlier models left a md5crypt type hash in /etc/passwd, however firmware AAVF.10
introduced these being stored in /etc/shadow. You may have some success reading this file by logging into the router as the "admin" user via SSH. You will need to crack the hash ( eg with hashcat), the password will be 8 characters long using characters 0-9,a-f (lower case)