Differences between ROO series

[afond]

Hi, after a few years without AP, i acquired a 15300 and ROO panda.
A few years ago I had a F-series safari which I sold, and next to a new box from audemars,
i found the rubber pushers and crown quit soft on the last I-series 26170.
I can put my nail into the rubber, where in my souvenirs it was quit hard on my F-series. Is that normal?
I also discovered a new typography on the datewheel, a few examples:

http://www.rolexforums.com/showthread.php?t=341310

http://4.bp.blogspot.com/-yRpp0meLtX...guet+Panda.JPG

http://i183.photobucket.com/albums/x73/emagni/035a.jpg

http://i38.servimg.com/u/f38/16/33/62/09/audema10.png

Do you know other differences between the F, G, H and I series?