All of my sketchbooks – and there are hundreds of them now – have remained unlabelled until very recently. They were, mostly anyway, dated and their contents were listed on the opening pages, but there was nothing on their covers to identify them. Some of those from the 1980s to the 2000s have no dates in them and very little written in them, but there may still be enough to date them, such as a drawn infant daughter, or a specific location that can be pinpointed to a particular time. Date and location, date and location, I say to myself now: easily done at the time, less so later on, sometimes impossible decades later on.
Part of the reason for not labelling them was not being sure what was the best method. I didn't want to use one system and then change to another. I have opted for a simple dated system: year and month that the sketchbook was started. Perhaps a simple numeric system would be enough, but the system I've opted for allows new sketchbooks to slot in easily if necessary. And each page can be numbered and added to the catalogue number so it can easily be identified and found: say, 2020.03.32.
In my imagination I can see spreadsheets of each book with every image listed so I know exactly where and when everything was done in an easily searched format, but really, life is too short for that. There is a balance to be found between organisation and creativity. I think time is better spent drawing and writing.