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You should be able to open it up and see. It's tough to say how big it is.
My two pulchripes are only about 3-4" and I sexed them easily by taking photos with my macro lens.
Here is what a female looks like...
And the male...
This is the male at 4" and the female is at about 3".
Oops, sorry. I didn't see the part about the tweezers being there for size. I think that they might be too small to sex without a microscope or a good macro lens.