Weird Orange Ring on Tortoise Shell

[Average Joe]

My tortoise was soaking in a tub today and I noticed a strange bright orange ring. I couldn’t clean it off so I don’t think it’s caked on dirt or anything. It feels just as hard as the rest of its shell and extends all around. Is it some sort of disease?

 

[Cooper horn]

It looks like new shell growth

 

[ascott]

My tortoise was soaking in a tub today and I noticed a strange bright orange ring. I couldn’t clean it off so I don’t think it’s caked on dirt or anything. It feels just as hard as the rest of its shell and extends all around. Is it some sort of disease?

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View attachment 243531

Normal.