This is one of the largest small watches you’re ever likely to see.
The Citizen 086884Y, also known as the Soundwich, was released in 1985 and is pretty much just a wrist radio since the watch part is about as basic as it gets.
The watch module just shows time/date/seconds, like a million other basic watch modules did at the time, but is interesting because it’s in a branded Citizen product. Citizen were well-known for making watches (and still are) but not so much for radios. There’s probably a clock radio or two with the Citizen name on it, but it wasn’t exactly their core business.
While there were other AM wristwatch radios, the addition of FM may have required a lot more power, or Citizen were hoping to make this a product where the user didn’t have to change batteries every week or so. So the battery-pack (on the left side of the watch) was separate to the rest of the module and is detachable. This meant you could have a lighter/smaller wrist device if you didn’t want to listen to the radio.
It came in a variety of colours, mimicking the walkman craze of the time. You could get a Soundwich in black, like this one, or in white, yellow or pink.