This is a third generation Game Boy clone, based on the Game Boy Pocket. Console features audio jack, audio control, contrast control, Nintendo link port, and AC port. The system runs a custom bios that shows "Loading" on startup instead of the Nintendo or Gameboy logos. The audio for games seems to run faster on these clones than on the real hardware.
Thanks to Trenton_Net for the pics and info on these, see more on this thread: