Chuck,
Oil bath air filters were an option for some markets such as Africa and maybe Australia because of more dusty conditions.When you open the top, there are three layers of fine wire encased in round trays with mesh. The air is sucked thru the bottom of the bowl which should be filled with engine oil upto the paint mark.
From the outside they look pretty similar except that the inlet on the oil bath is towards the passenger cabin while on the paper element type, the inlet is facing the grill.The oil bath casing is double walled and much heavier.
naj
'Kloines Scheisserle'
65 230SL
68 280SL