I admit that many moons ago I could be found with my Ian Allan books collecting the numbers of A4s, Black 5s and their like. I know there are still a devoted band who carry on the tradition with EMUs and Pacers.
I was recently waiting on a bleak platform with only a small wind swept shelter as rain and sleet began. 2 or 3 sheltering there were such people and they'd notebooks mostly full of freight locomotives. However, when a freight train rumbled through I was amazed to see one chap frantically noting the numbers of each wagon. Surely that must carry the hobby to extremes!
Is there a book of freight wagon numbers to record them in?
Go to somewhere like Stafford, Doncaster or Carlisle and you will see loads of wagon bashers. A much rarer breed is the container spotter, collecting numbers of shipping containers on freightliners and intermodals.