No blotching on the belly suggests it is the nominate spider subspecies P.a.arachnoides or the northern subspecies P.a.bryoogi. If there is no movement of the front part of the plastron, similar to a box turtle, you are looking at a northern, if it flexes easily, the main species. I have an adult male that is well over a decade and is only about a half inch longer and averages 165 grams. If I were to guess age group, I would think this one is a young adult since the yellow pattern that typically edges the carapaces scutes hasn't begun to grow in yet. As far as gender, my guess is female, but if it is indeed young, that could still go either way.
Anymore questions feel free to message me directly or post them here so that others can learn or provide better answers ;-)
The photo that I attached is from a book and it shows the bellies of all three subspecies, Northern and common have no markings, southern have blotches on the bellies.
Beautiful animal. It’s hard to tell if it has a hinge on plastron but appears to. It looks like a P a a female to me. Having raised them for a decade, I’m fairly confident on female Paa. Congrats on an amazing animal. Care for her well!