I am not quite sure about Tresors being targeted at the less affluent areas of the world as they seem to have been marketed with Connies, SMs and Geneves (at least in Western Europe anyway – I don’t know about the US).
I can understand that the Tresor would be marketed below a gold Constellation as the latter is superbly finished and always a chronometer but whether it is below a gold Seamaster or Geneve is debatable.
As well as being fitted with non-chrono manual cals 260/280, Tresors were also fitted with chronometer rated 351s (the same as Seamasters) and 354s (the same as Constellations) and non-chronometer 491s/501s (the same a Seamasters) – I am not aware of a chronometer rated Geneve. Tresor cases were virtually always a heavy, solid 18kt gold with clip-backs - the same as Connies and SMs of the time - so waterproofing would have been the equal of those.
As far as I can see, the only difference between Tresors and Constellations, Seamasters and Geneves would be in the dial.
Cheers
Andrew