His shell looks almost like new, since most of his scutes have fallen off already. When the scutes fall off, they reveal the newer, fresher shell layers underneath. The colors and patterns on his shell looks brighter and fuller, almost like he went through a time machine and got younger. By simply comparing the appearance of shell scutes to each other, you can tell which ones have recently been shed and which ones are going to go soon – basically it’s comparing the dull shell scutes vs the bright.
Here are some photos of the current state of of his shell: The parts encircled in red are shell scutes that my pet turtle still has to shed.
See the difference with the still be shed areas and the areas where turtle scutes were recently shed?
If you look carefully at some turtle pictures of his neck, you can see the scarring from when Cinderella, my other pet red ear slider turtle bit him.