Eager beaver 2.1 chainsaw chain adjustment screw

[chainsawnewby]

Hello,

I have an older eager beaver 2.1 power mac 300 series chainsaw.
The chain has gotten loose, and I need to tighten the chain adjustment screw.
It is inside the black plastic housing and I can clearly see it underneath.
The problem is I have no idea what kind of screw it is.
It looks very small and a female type.
I have tried every small screwdriver and hex key I have and still cannot find the right fit.

Does anybody know what type of screw is that on this model?

Thanks.