That is a gameboy micro, I have green one. I used to like to bring it in my pocket when I have to play on my work breaks. lol The screen is so small I can't play for long time without hurting my eyes and buttons after a while make finger suffer but I still love it!
Which is why i also have the Gamecube adapter (attaches underneath and has a loading disc) to play them, legit accessory.
Mine came with faceplates and they are all limited edition...worth around what i said even on e-bay.
i can't bring myself to sell it regardless, I just happened to grab it at gamestop on a whim because I love NES, I owned a second GBA at the time...that one I did get rid of because of the NDS and Gamecube adapter.
You can't find the GC Adapter anymore these days either without some luck sadly. Its not the best on HD, but its better than the tiny screen.
Fun fact:
The Nintendo DS (without a GBA slot on it) requires a hacked DS Cartridge
because the GBA actually has more memory than it does, the homebrew cards all have a memory chip in them to make GBA emulation Possible...when i attempted to make that game on it, I started by trying to make a GBA emulator and realized it was impossible because of the specs on a DS.
Thats why they removed the GBA feature in the some models, to cut costs.
I still think the GBA was one of the best systems ever made, just for the diversity of games they put on it from all Nintendo systems before it, which is probably why it needed all the memory.