Pending your pics, I would say the manifold on top (mostly, depending on the exact inclination of the compressor) or the front seal.

The manifold is held on by four allen head screws, you can probably only see two of them. The hoses are held to the manfold by a single screw, usually, on a clamp plate with the screw between the hoses. Those o-rings leak, too, when they get old.

Any AC parts supplier can get them for you, they fit a Nipondenso AC compressor, probably a 10PA15C or 10PA17C. I would guess they are the same on all Nipondense compressors.

A leak tester would be very handy here, would help locate the problem. With that much oil on there, you should be able to hear the freon hissing out if you connect a can of R134a and blow vapor into the low side (about 50 psi).

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!