Sorry there's no answer to this. I'd like to know too.

I went looking last week for a used set of AP1 irons to replace my G15 irons. I like the feel of the G15s, but they are heavy and modifying them to be longer for my height, (6'7") isn't possible without adding much more swingweight or going to graphite shafts at very high cost, even at my pro shop cost by sending them to Phoenix. They said at 1" long, they couldn't keep steel shafts under D7. So much for their fabulous fitting program.

I looked at some original 2008 AP1s and some 2010 AP1 710 models and chose the latter just in hopes there would be something better without knowing what it might be. Since they are lighter than my G15s, I have room for an inch of extension and lightweight grips getting me only to D3, a weight that is still playable for my old bones.

I know from another thread that the 710 series have conforming grooves, but other than the cavity shape on the back of the clubs, I don't know what different technology there is to our benefit. I just know I love them.