When it comes to object-collecting (there's a name for it, of course, which escapes me right now), watch-collecting would be among the top of the list of objects being collected. If you are a watch-collector, what kind of watches do you collect? Some people collect by make, others vintage, others by era, and many other categories.
A friend recently acquired a Lange Sohne, a German watch. I was told the entire Lange product line is desirable and in limited supply and the gold versions of each model are easier to find than the platinum versions.