I think female but don't take my word for it.
Is the plastron concave at all? Our female has zero hint of concavity. She was only 10 inches or so when we took her in 5 years ago, only weighed 9lbs then & we pretty much figured she was female. We know for sure that she is at 70lbs.
(she laid some eggs so there is no doubt lol)
I know a male her size who is very concave on the plaston, it's very obvious in him.
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PHRatz