@BackdoorHippie if I remember correctly, someone mentioned having a friend who works for Nikon Canada who confirmed they (the Canada division) was installing the shutters from the D610 into the D600's that were sent in for the oil/dust problem.
It was me that heard that from a Nikon rep. So, in a way, it is hearsay. What I was told is that the problem with the shutter supplier/manufacturer was solved when the last batch of D600 were produced. So, I don't know, but it could have happened that Nikon supplied replacement shutters that were defective for a while to their outside (US, Europe, Canada) subsidiaries. I know that some of you have had huge problems with this model, but I "think" not all units were affected. As I can only speak for myself, I can agree that I got dust (more than usual) when I was in Vietnam (first 3,600 shots), but after cleaning the sensor, the problem has completely disappeared. My 600 is now as clean as my 7000 or 700. I guess I must have been lucky. Such things happen when you lead a good life