2405 Diaphragma -blue- from my 4333A

[Toms Studio]

Hi,

yesterday i buy 2 beautiful 4333A in like new condition.
I am very curious, so i open a 2405 to see the data stamp on the Diaphragma.
I was a bit surprised, because the Diaphragma is blue and no Stamp on it.
All (10) other 2405 i open years bevor, had gold Diaphragmas with data Stamp.

I am sure the 4333A Boxes never open bevor. I have them from 1. Hand and they stand all the time in a livingroom. And how i can see the 2405 never removed bevor.

Have everybody see a blue Diaphragma like this bevor?
Maybe JBL use it in a serie of 2405?

Thanks for help.