Well, Subfallen, I don't know how to measure really. But honestly I haven't been very physically active for a good while and my hands were ALWAYS pretty weak in the grip department(though I have high endurance for some reason), but I still was able to get most of the way closed on the #1 on my right hand. It's probably pretty fair to say that if I can do that -- sorry to say -- almost everyone else can too. I'd actually be surprised if most people couldn't do better, because my grip strength is truly crappy.
That makes me think that most anyone could start with a #1, and skip the Trainer model. Especially since you can actually cheat your way if the #1 is a little too tough. I'll post a link on how to do that, and how to train with them.
The #2 is a big leap up from the #1, from 140 up to 195 pounds. Lots of people supposedly have to train up to that one, as it's the last one you can do without having grip so strong you get certified for it(and that certification/ability is NOT common). I think I'd recommend just dropping the $20 on a #1 and if you find it too easy, well, it's only 20 bucks, and you can still train on it. Then you can then order a #2. Or just order them both. Skip the trainer.
I think more should do this too. It's not a pricey thing, and as far as physical fitness goes, it doesn't take a gigantic commitment. I mean, you could be a big fat slob and still have a killer grip, or work up to one. You don't have to be a gym rat or anything. And it's cool that you can actually measure your progress, for bragging rights with your buds. Or even get certified, if you really want to go nuts with it.
Here's that link:
http://www.dragondoor.com/articler/mode3/123/
Took me only a few minutes to get a little sore!