Unknown hole near oil pump drive

[Coyote]

I'm no expert but I don't think that hole is part of the program. It looks to me like the casting was thin in that area and broke through while machining. I imagine the floor of that hole is thin as well.
Judging how the pump works, I don't think this will affect anything.Or might it?

[Cliff]

Just checked one of my upper case halves and that square hole is there too! It's not machined in, it's cast that way. Probably a drain hole to allow any oil that comes up around the pump drive when it's turning to drain back.

[Coyote]

That's the only thing I thought it might be. It just didn't look like it was intentional.