That video has been circulating the internet for a while now. I think its a video done to make it look like that guy is squatting alot more than he really is.
A couple of things just don't seem right to me. First off, I can't see collars on that bar. If you load a standard 1000 lb capacity olympic bar with 45 or 50 lb plates that full, the plates will slide off the end of the bar due to the weight of the plate and the whip while you squat, especially with that degree of bar flex. Those plates hardly separated. The only way I've seen that happen is with a bar using those plastic/plastic coated olympic lifting plates that are all of the same diameter.
Second, some people say its heavy becuase of the bar flex. I've worked out at some commercial gyms where you can get that much bar flex with only 315 on the bar beause the bars are pieces of shit. To think the weight is heavy becasue the bar is bending doesnt mean anything without knowing what kind of bar that is. Shit, I know of a Golds Gym where they purposefully got "lighter" bars so that the gym members would think they are squatting more because the bar bent as they squatted.
Third, those are supposedly Ivanko plates based on the comments below the video.... I can't for the life of me see the groove that all of the Ivanko plates i've ever seen/use have on the 25 kg plates. I also am not aware of Ivanko producing "gripper" plates like those are. I've tried and tried to read the weight on the inside of the let plate. I can't do it. Ivanko plates can be read from several feet away, even wiht shitty video. I don't think they are the plates that others thinks they are, so who knows what they really are.
4th, the spotter is damend close to that guy lifting. He could practically be helping wiht the lift as close as he is and how he's hanging on. If you watch his calf flexion, it seems to be quite a bit, but that could just be the individual.
Finally, look at the lifter himself. Thats thought to be over 700 lbs. Think of the lifters that size who've lifted 700+ lbs in competition. At the end of the set, they look like they've lifted over 700 lbs. Their faces are red, veins are bulging, they are shaking., they are sweatting. He does three reps, then stands up and walks the weight in like it was no big deal. That alone makes me really doubt the weight in this video. I'd believe 315 to 350 pounds way before I'd believe 350 kg.