Many reconstructions has been done of the megalodon jaw. The first attempt was made by Professor Bashford Dean in 1909. But in 1991, two shark experts, Richard Ellis and John E. McCosker, pointed out flaws in previous methods. The following are some of the versions of the famous jaw.
Apparently this is the biggest megalodon jaw in the world, however it's not very realistic.
This jaw, we've seen in real life in San Fransisco not long ago. It's a quite good size.
So is this
These two pictures (in black and white) showing the first reconstruction, from 1909, is made of real megalodon teeth, which we think is quite a waste, since the jaw doesn't match the reality. It's rather big. The dude sitting all by himself is professor Dean.