I'd say that's a Jersey Giant, 10000%. The legs aren't showing any hints of whiteness near the pad that would indicate Australorp, and hatchery SLs aren't large birds as a general rule (built for egg production, not meat/size).
I'm actually really excited to think I might have scored a Jersey giant rooster out of a straight run bin LOL! I have always wanted to have one and see how big they get. I need a big Roo right now, I have a little banty roo and BR cockerel but It would be great to have a big boy out in the yard