What is this N64 Cartridge thing???

Hello, I found this weird N64 pass thru cartridge a couple years ago at a flea market, and have no idea what it is. I have no idea how to open it without destroying it since there is no screws or other obvious ways of opening it. The only use I have found for it, is that it works as a pretty good pass through adapter to let me play my Japanese N64 game on my US N64. Plus it makes my cartridges sort of look like the large N64 Dev Carts.
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I have one of those, it's to play pirated N64 Games, it's used to pass the CIC check.

 

never thought n64 pirate games does exists :O....

 

So with this I could play PAL games on my USA system?

 

Far as i know it is also a region changer catridge, i used to have Sin and Punishment and used one of those cartridges to play, the seller said that i should be careful to not overheat.

 

I doubt it but who knows. There isn't a rear slot to load CIC data from PAL games.

US vs JPN in either direction works so perfectly as it is, using an adapter doesn't really make sense for long term use. Storing away the dust cover will work too if one would rather not cut it.

 

Thanks for your guys help, you are pretty much confirming what I believed it was, it is always good to have a second opinion.