The Circle looks much more like paint than like a moisture indicator, indeed.
When I looked at it, I paid a big attention on it, and I opted for a paint circle, rather than a moisture indicator.
As for the cases now,you mainly have 2 kind of cases, the sandblasted ( rarer ), and the polished.
On the military ones, I mean the TR 900, the MIlspec, they are all sandblasted, while on the Bunde, the case is polished.
Best,
Nicolas