Extension speaker unit with built in audio filter.
It sounds much better than the internal speaker on FT-One and on the FT-857 and the switchable filters provide an improvement to the audio quality especially when monitoring SSB.
It has two selectable inputs, selection button on front, sockets on the rear, and a socket for head phones on the front.
Mine does not include the phone patch as per the manual that I have but this is no loss as it's a feature that I would not use, even if it was legal here.
It’s a bit grubby and has a few marks on the top surface, but as it was picked up at a boot sale for about £10 I am not complaining.