I sent both my D3s and D3x in for cleaning, and to fix the vertical AF-ON button on the D3x. When I removed the RRS L-bracket I noticed an oil film on the base of the L-bracket. I don't know which camera that L-bracket was on. The oil film is the footprint of the base of the camera. It is not water.
The cameras reside in a Pelican case or on a shelf in a closet. I have never spilled anything on either camera that I know of.
This is the first time this has happened and I am just curious as to the origin of the oil.