Under the centre boss label, a/small depression. Or 'cup' a drop of motor oil.
Many years ago a chhum had a 'Tiny'. Rememder those?
The fan on this noisy-he called the engineer'who took a look see, returned to his car and came back with the engine dipstick with the end INA rag, and dripped the oil into the 'cup' as above----job done.