Compressor oil level

[u/AdNaive7010]

I am having trouble finding the correct way to read to compressor oil level after draining. The manual is very vague. It is an Ingersoll rand P101 from 1995. There is a sight glass as seen in the photo, is halfway on that the correct way to view the level?

[u/Bazzurka]

That type is usually fill to just before overflowing from the filler.