Radiomir: 30m vs 100m?

[Fredrik]

I am currently looking for a Radiomir and I am a bit puzzled concerning the depth rating for different models. Seemingly identically cased watches are sometimes rated to 30m and sometimes to 100m.

How come?

There is a nice 249 at the moment for sale here, but is for some reason rated to 30m while the 232, released simultaneously I think, is rated to 100m.

Am I missing something glaringly obvious, it would not be the first time...