It's a label swap. The holo labels are very easy to take off. You just need some super glue, swap the board and you have yourself a grey MM cart.

So you don't think this could have been a replacement cart sent by Nintendo? They did something similar with another release. 

It's been discussed quite a number of times. I don't believe Nintendo offered any kind of replacement for Majora's Mask. While there are a few revisions of MM. I don't think there was ever a revision that had game breaking glitches or bugs.

I also know that labels were handed out either at events or game stores back when the game was released.

Ahh alright well thanks for your help!  

I've seen a couple of these from different eBay sellers recently--so it's for sure not an official variant??

You can tell that the label is off center. Definite label swap

Nintendo either sold or gave away the label as a sticker actually at one point. One of these "stickers" pops up on ebay every once in a while. You can literally slap it on a gray cart and it is Exactly the hologram label. I would imagine, this is what that is.

EDIT:There's a thread about this somewhere in the depths of NA

http://s885.photobucket.com/user/...


My bad it was a promo pin for gamestop managers, same deal though, snag the sticker on the pin and slap it on a gray cart