"P" adapter for RB

The Polaroid back that came with my recently acquired RB seems to couple to the camera (after removing the rotating back adapter) without benefit of the P adapter. Is this correct or do I need to seek a P adapter?
Also I notice that the Polaroid back has a groove on the forward face but there's no seal in the groove. Does it require one?
thanks,

Larry

You will probably find that it already has a P adaptor on it if it already couples to the back after taking off the rotating back adaptor. The P adaptor has two silver 'L' shaped lugs. If you push these down, the P adaptor should pull away from the polaroid back. If it does, you have a P adaptor! I read somweher that later polaroid backs do not have/need a P adaptor but couple directly to the camera after taking off the rotating back, but I can't confirm this as I only have an earlier one. The groove does not have any foam seal in it, so you dont need to worry about it. Welcome to the world of RB polaroids, they're wonderful. You do know that Fuji instant film is fully compatible with them?