RE: Serial question

The reason you didn’t see the CO 767 in the book is because it is too new. I assume you are using a civil aircraft markings publication of some description.

The problem with books like these is the fact that they go out of date too fast. New airliners are being delivered all the time, although the airline will usually reserve a particular registration prefix in anticipation of new aircraft, in europe anyway.

The North American register is difficult though, airlines often change the registration last minute and think nothing of changing an existing aircraft reg’n, which may be a reason why your NW DC-10 didn’t show.