This is one of the original version of the Nintendo Wide-Boys (Wide-Boys are devices that are plugged into either an NES, SNES or N64 so you can see the Game Boy game on a TV, thus saving developers eyes from having to stare at the little screens all day long). Says WIDE BOY-3(B) on the circuit board.

This version pretty much has the entire Game Boy on the large circuit board (there is very little circuitry inside the Game Boy itself, it's basically just a controller). On the bottom there's a typical cartridge connector designed for the top-loading style of the original Japanese FamiCom system.

It normally has this large, black plastic cover protecting the circuitry.


And here's the backside with the top-loading connector for the FamiCom.

The following two images show the inside of the Game Boy controller with a circuit board from a real Game Boy to the right of it so you can see the difference in the internal circuitry (which is pretty much non-existent when compared to the real Game Boy):

Component side (you can tell from the volume knob that the circuit boards are both the same-side-up).
The DMG-CPU chip on the real board can be seen on the Wide-Boy in the top picture.


Solder side.