The crew had identification books (idk their exact name off the top of my head) that showed their previous discharge and their status (aka good worker, great worker, bad etc...) With that there were lists of deserters.
The crew's little books were called Continuous Certificate of Discharge. It became traditional to give only two ratings on discharge. The sailor was either rated "Very Good" or the master "declined to report". The latter meant he was really bad in his work or his conduct. The masters had little rubber stamps made to print "VG".