from sigcurious: An E2 is a minor variation on the base model 229, the only difference would be the grips and possibly the slim trigger depending on when it was made(they call it the short trigger, but slim is a better descriptor and saves confusion with the SRT).
He's got it exactly right. Don't confuse the new grip style with E2. While the E2 model STARTED the new grip style, you can now buy the standard P series guns with the new grips. This doesn't make it an E2 model. If it's an E2 model, it will say so on the slide. I have a 226 that is the new grip style (and has a short/slim trigger) but doesn't have the SRT and is definitely not an E2 model but instead a "standard" P226.