On my distributor (051), the oil cup assembly consisted of two parts. The base is the part that press fits into the distributor casting and has a fill hole. The cap is permanently crimped onto the base and has a fill hole that matches the base. The cap simply rotates around on the base. To add oil, rotate the cap until the two holes line up. When finished, rotate cap 180 degrees to cover the hole in the base. The cap never tightens down but should not be very loose either.
