No, that's not it. The WiiU gamepad dock looks different. It doesn't have that weird indentation that I can't understand what is for.
Also, Haloman told me it has no markings on it, so it's clearly some sort of 3rd party dock. But for what?
But there is no charging port and that design with the roundedness wouldn't fit the 3DS. It might fit the XL but I don't think even the XL is that rounded. It looks like the XL could actually fit nicely, I just checked some images.
However, in the orientation that it would fit (the top edge of the 3DS does not have rounded edges) that indentation would be nowhere near the charger port. I'm thinking the indentation might be for the headphone jack, and that this is actually a holder to play Kid Icarus and similar, but it seems awfully vertical for that.
Yeah, that's what made me think it's not just a cable holder, even though it looks like it. Maybe there's space enough that you can plug it in the 3DS but it still seems rather useless since all it does at that point is hold the 3DS in an upright position which I guess looks prettier than just laying it on the table but it doesn't serve a purpose.
It does not seem to be designed for the 3DS (or XL) charger plug though as it seems to be designed for something with a very flat connector. Like a male USB connector without the metal housing, but that's probably too big. I really can't think of anything else that uses a connector like that. The Apple Lightning connector is similar to that. But the iPhone doesn't have that rounded edges anyway so that's probably not it.
by how it looks, it'd be the 3DS (XL) base platform.
Say, 3DS (XL) has a piece of plastic that acts as a base for it. Then that one goes all way down that narrow hole of plastic, and the smallest hole that goes from the outside makes the cable (charging purposes?, data?) go through. (by how it looks, it could be any handheld stand).