Case 1170 rescue with unknown oil port

[Dirt Don]

We rescued a Case 1170 the was sitting a long time. After getting it home, changed all fluids and filters and fresh batteries.
Went to start and it was close but somehow missed a small plug missing from a small port near the oil filter the started leaking oil. Obtained a plug, but does anyone know what this port would be for so we are not missing something?

 

[Case Nutty 1660]

normally that one is plugged, some one may have installed a sensor for a safety shutdown,, 1/8" pipe plug