AFAIK, such a thing doesn't exist. Maybe there are some hiding in one of Nintendo's facilities or at some dev studio if it exists. Right now it seems, they are possibly nonexistent if Nintendo decided to not make one at all.
They do exist, along with 2DS pandas, and new 3DS(XL) pandas. There was a japanese 3DSXL panda on ebay awhile back. Afaik, any Nintendo handheld running a pre-release version of a game is a panda(test unit). So go to game demo events
Yes, the whole 3DS Family has a Panda Unit, but from the outside, only the regular 3DS differs. All the others have one of the standard colours, with almost all of them, having a Sticker on their back. For the ones wondering: I've quit my Game Dev activities, last year, now I'm a Freelance Web Programmer.
I won't comment on the thread due to NDA, but I have to ask: why the hell would you quit game development to do web development?
Well, it's not like I wanted to quit, I had to quit. I had a lot of health issues, last year, but once I came out of it, I started to look into Mario Kart 7 ROM Hacking, so as a result, returning to Game Development was no longer an option (except as a hobbyist one, of course).
The whole point of this thread is that I'd like to see a photo of one unless they just had a different label.
You can also get a Photograph of a Grey/Black 3DS XL, and not take a Photo of the back, as it's the exact same thing.
Here are some pictures of the one I have. There really isn't much special about them on the outside other then the back cover and it's box.