Two different phase plug revisions of JBL 2446J comp driver? (incl. pictures)

Hello, I discovered yesterday, while cleaning my 2446J drivers, that they actually have different revisions of the phase plug! I always though the slight differences in FR was due to other elements, but it's the phase plug after all after some testing.

The serial number of my drivers are (named A and B like in the pictures) are pretty far off: A) 16992 B) 01679

Are the two revisions of the phase plugs in 2446J to your knowledge?

Another option is that someone has put a 2446J backside cover to 2445 body? I bought the drivers from Ebay couple of years ago and they both are in very good condition and visually identical except the different phase plug.

I find the B option to behave better with my Truextent 'phragms and I'd like to find another piece of those. How do I find correct pairs for these drivers? :)

Here are the pictures and a quick draw. The A driver seems to have straight slits while the B has curved slits and they are all facing directly downwards to the throat.

http://i817.photobucket.com/albums/z...pswitfvwit.jpg http://i817.photobucket.com/albums/z...pshm6ym9tm.png

B is correct for 2446 (coherent phase plug design). Back cover swap is most likely.

Thanks grumpy, is that 100% sure? They measure somewhat ambiguous, one could also think the B is the 2445 based on my measurements (comparing to the measurements seen here where both 2446 and 2445 are measured with same horn/diaphragm).