This speaker accessory is intended for use on an Ultimate 64 board. It mounts near the cassette port and will reproduce the floppy drive sounds. PCB color is green.

More details see: https://ultimate64.com/

This is based on open source release of the speaker: https://github.com/GideonZ/ultimate_releases/blob/master/U64_Speaker.zip

Thanks for Gideon Zweijtzer for open sourcing the hw design. U64 motherboard in second picture is just for demonstration where the speaker is installed.

Shipped as unregistered priority letter (in cardboard letterbox).