when I said:
The moisture indicator didn´t appear in any Ff since 1960, with the Milspec, like in the Bulova (one year before, aprox).
Here are some proofs...
*LIP Blancpain, 1954-1956, 34mm, AS 1361.
LIP Blancpain, 1954-1956, militar model of the CIEPM, 35mm, AS 1361,
The caseback...
AS 1361...
And the one in your post is another (or best) example.
So, definitely, Blancpain used moisture indicators in its models before the end of ´50s.
Probably the first in use this moistures???. I think so and, sure, before than the Bulova.
And, for your words... I know the guy who planed to Madrid???. This guy made what he must made! ))
Best, hermano.