sexing box turtles

[TLWR]

At what age are some sexing indicators a somewhat accurate indicator of gender?

I have at least one with a very nice domed carapace.
The two I picked up today have a cloaca very close to the body - one of those may also have the nice dome, but I don't recall who I picked up today.
I usually leave them alone, but figured they will be digging in soon, so I scooped up a couple today while they were out and about. They are 2 years old.

 

[Berkeley]

Age is not so much the factor for determining sex as size is (basically, not how old, but how big is the turtle?). Growth rates vary due to diet and nutritional uptake.

Domed carapaces (particularly if they drop sharply over the tail) are often an indicator of females, as are cloacas close to the plastron. Pictures would be most helpful. If you have some and can post them, more opinions could be offered.

--Berkeley