My current roommate closed a #2 with the normal "I don't know what I'm doing" set his first time touching a gripper (17-18yrs old). He never trained grippers. A couple years later when he was maybe 20yrs old, still with no training, I busted out a #3 that one of my buddies lent me (around 153 Eric Milfeld rating) when he was over at my house, and the man got super close to closing it with the same "I don't know what I'm doing" set. I went and put the #3 in a choker for him wider than parallel so the choker wouldn't assist at the close at all. Closed it myself to make sure it felt normal at the close, gave it to him, he mashed it. To this day he talks about my reaction to that incident. I could not believe that he closed it like that.
He didn't weight lift at all. He worked landscaping, but to be honest, that type of work won't make you THAT strong. I was in that line of work myself for a couple of years. His stats: 6'2-6'3" tall, 230lb but doesn't have the thick, farm boy look that a lot of guys have (his forearm is MAYBE 12"), his hand's span is at least ten inches but it may have been 10.5 I can't quite recall, and his length is 8" maybe 8.25". Hand not that long, but the span is impressive.
I'm not super surprised when I see a guy with Jonathan Vogt's build close a big gripper (thick, meaty hands and forearms), but my buddy with his relatively thinner build blew me away. His 5 rep bench max was 135. Weird. Probably a 160-170 bench max, and a 153ish gripper close. I was blown away. Note* major respect to Vogt on his #4 work, definitely not trying to degrade that at all. Very impressive.
As with most guys that can do ridiculous stuff grip wise out of the gate, he was strongly right hand dominant. His left wasn't as strong.
He is now (23yr old) lifting and training for armwrestling with me. He's made good progress since he began training. After seeing the #4 comments from people, I might try to get him into grippers (at the risk of his armwrestling career) because he just might have the gift.
Another buddy of mine (my old training partner) was also pretty freaky. He closed a #3 (the 153ish one) while he was 17 or 18. He trained for 1-2 years, but he was also a "normal" guy at 5'11" 180lb 7 3/4" length maybe 9ish width. He had one of the worst disparities between right and left for a while: R: #3 L: miss the #2.
Those sick strong people are out there.