Perfect comparison photos from Mordimer. New on the left, old on the right. On the new ones the Piezo pieces are wider, and there is only really the one contact point for the string (on the piezo). The old ones touched the saddle opening and then the piezo piece on their way out of the bridge.
I noticed the difference when I bought my JP7, which was made in 2014, compared to my 2013 JP6.