First, thanks for playing Eterna-Fan and understanding the spirit of my question. Obviously, such a question is always 'too general' because ultimately you have to go to the level of an individual watch to assess it's value (condition etc.). But, again ,the question was really in the spirit, of 'in general, all other criteria equal - i.e. assuming let's say mint condition etc.".
Nico's point about 'groups' of calibers and models wtihin a brand is a very valid one. I also think that for some brands certain watches (Longines 13 zn, or Zenith 135) or for example 'hyped' or richly valued, others over-looked. That's a very fair point. I still think that as a trend it's possible to judge if certain brands are currently under-rated, fairly valued, or 'hyped'.
Here my take - again, subjective and debatable of course, it's not scientific: (I have added some brands based on your suggestions)
1. Zenith - 4 for El Primeros, 5 for all others, 7 for Cal 135s
2.Longines - has changed dramatically over last 2-3 years: 8 for 13zn, 6 for 30ch, 5 for all 'time only'
3. Movado - 6 for 90/95M, 5 for rest
4. JLC - 8 for Polaris (I know many in forum will disagree, but I think it's a hyped model - although I have one myself and love it), 7 for Geophysic, but 4 for many others (Futurematic, Quatermaster)
5. Rolex - 9 for Daytonas, 10 for PN Daytonas, 6 for Seadwellers, 7 for Submariners, 5 for Milgauss 1019/Explorer II
6. Patek - 9 (don't know enough though)
7. VC - 4 across most vintage models
8. AP - 3 (for vintage 50's/60s time only), 5 for A/B/C Series Royal Oak
9. Universal - 3 for Polerouters, 5 for chronographs
10. Eterna - 3 for Kontikis, 4 for rest
11. Heuer - 4 for 1960s Carreras, 9 for Monacos, 8 for Silverstones, 6 for most Autavias, 4 for Seafarers
12. Tissot - 4
13. Omega - 8 for some chronographs (33.3), but 4 for some seventies models, 5 for Constellations - overall 5 (think still fairly valued)
14. Eberhard - 6 for chronographs
15. Minerva - 4 for the old original 40s chronographs
Again, by no means scientific, jsut wanted to trigger a discussion - and of course, it always at the end depends on the individual watch. But I am sure we all have a 'framework' how to think about a brand when we hear the name
RDL