Farmall B transmission gear oil level ?

HI Guys
Does anyone know how to check the level of the gear oil in a farmall A /B transmission. I drained it and can measure that but I bet it was low. The final drives were empty !! Apparently this machine was painted 6 or 7 years ago. None of the plugs have been out since that time, tranny, final drives or oil pan.

Found Rudi's Super A manual. I will see If I can find it in there. Thanks Rudi

Level plug is on the left side,near the brake rod.

Thanks Jim I appreciate the help