JBL 2441 Diaphragm

[John]

Hi Did the first batch of 2441 diaphragm's from JBL have a dimple in the center and then later change to a small round foil sticker in the center instead of the dimple If this is indeed the case how long was the 2441 dia. in use with the dimple before JBL went with the foil sticker and why

[John]

Any one willing to step forward

[Guido]

I only know the ones with the foil sticker.