Each camera puts a camera-specific folder on any card that it sees. It puts its files in that folder, and moreover it does not ever look at any other folder. The only way that a D3s would see files from another camera is if the other camera is another D3s.
Moreover, if you are using the camera to download the files to the computer, it will only do that for images that it sees. More precisely, this means that if you use the card in two different models, each will NOT download the others' files.
This is not true of a card reader, because the computer is able to look at the entire card, regardless of names or models. So for example since I use a card reader for all downloading, I never have the problem of not seeing a different model's files. The computer (Mac at the moment, but in the past was Windows) is able to download them all.
_____ Brian... a bicoastal Nikonian and Team Member
My gallery is online. Comments and critique welcomed any time!