It is a genuine Nikon part with original case and plastic bag. Although I used it often, it is practically like new as I take great care of my gears. For example, I always put my RA viewfinders in the plastic bags before putting them in their cases to prevent dirt to reach them since the case isn't totally hermetic (I hope this word makes sense in English ). I also use the plastic bags to put my regular eyepieces in them when replaced by the RA viewfinders, such a good habit makes these small pieces harder to lose.
The DR-6 is easy to install (simply slip it on) but also easy to remove, so one must pay attention when walking in bushes with the RA viewfinder on. It is very helpful for low -level work, but also in difficult positions. For example, I remember how I could have not been able to take some rock photos in Alabama Hills without it simply because I was on a steep slope with an almost acrobatic position between big rocks and couldn't place my eye behind the camera...so I used the DR-6 sideways to compose properly and adjusting my tripod. Same thing to take a bird photo from behind a high bush, I extended my tripod so the camera ended up about 6" higher than my head (to see above the bush) and the only way to compose was with the DR-6 upside-down on the camera. Whatever the orientation of the DR-6, the image is always upside and left-right OK.
Don't hesitate to send me a private message if you need more info, we could even talk on Skype, Yahoo or MS Messenger