@jcboy,
Yeah, your tortoise's is/are a bit still in adolesence so they/it has some growing into the shell to match the other photo's tortoises age...etc.\
Another theory cold besome genetic cross-breeding with another tortoise type? Or perhaps slightly different diet type as it was growing (too much meat early in it's development) I read on one of the info sites where in some cases they have to be weaned away from a high amount from meat in their diet early in their growth and be on primarily veggies as they become older. Right?