Pair it with any device capable of sending Bluetooth audio, and connect it via a 3.5mm analog plug to your old analog amplifier. And voilà! You have now extended the usefulness of your old analog sound system, for a very cheap price. In our case the analog cable also needed a stereo adapter on the other end, to two RCA plugs for the left & right channel inputs on the amplifier.
As can be seen in the photo, it has a standard Europlug contact so it plugs directly into a 240V Europlug socket (or alternatively a Schuko socket), which makes it very convenient. As a bonus it also has a USB charging socket (1 ampere). I'm not sure how useful that is in practice, but it is certainly a nice touch.
Bought from Swedish company Clas Ohlson (product link here). I haven't yet identified the original manufacturer.