I started 'collecting' issue number information on a few UK MOD models that interested me about 5 years ago, Lemania's and W10's mostly. My reason at the time was to try to understand quantities and batches better because there were so many different watches and markings involved that it was quite confusing to a layman when other members had extensive knowledge on the subject.
I use a simple spreadsheet and don't log owners information or even the source as all can be found via the internet or in Konrads excellent book. I'm hopeless with computers and could not manage to keep the 100's of photographs either, unless a particular watch interests me for personal reasons, that is.
I guess I'm in there with the 'train' spotters and 'aircraft call sign' number collectors and certainly make no claim to be an expert in military watches.