I saw a guy come into my gym in work boots and jeans.  Looked like a construction worker or something.  Loaded 315 on the bar and knocked out 8 reps with no warmup.  Then did 405 for 8 reps.  Then did 455 for 5 reps.  No spotter, no signs of struggle.  After that, he quietly put the weights back, got a drink from the fountain, then left.  Back to his work truck.  It was lunchtime.