A battery powered sound playback machine.
The case is an old German T & N telephone switching station from the 1960s. More info about these gems of telecommunication history can be found on Michael Keller's page.
The circuit board is a custom design based on at Atmel ATmega328p microcontroller. Sounds are read from an SD memory card in uncompressed wav format. Audio output goes to a 12-bit D-A-converter, a custom amplifier and 10 W speaker.
Code is available on Github.