Just noticed - when did Iframes change?

[Aegis]

I just happened to hold up two of my Iframes together and noticed a few differences. I was trying to use a grip frame screw from another mag and it would not seat due to the curve of the front guard. Obvious differences:

Straight front on trigger guard vs. bent front
Milling in area behind trigger
dimensions flat spot at grip frame screw

When did this change, and did it make any difference other than cosmetic?

[rikkter]

far as i know it changed quite a bit ago to compensate for foregrips not being able to fit correctly because they would press against the trigger gaurd.