Casio W400 my 1st Marlin

Today a lot of "new" watches arrived at home. Let's start.
The first one is a Casio W400. A Marlin watch with resin case, screw down back and the well known 106 module (same as the classic H101).
The watch is in quite good condition, I don't know the age of the watch, but the production of this model started on the 1980!
To clean the watch I've opened the screw down back and removed the module.

 The "speaker" of the watch is not placed on the back as most of the Casio watches, it is at the front! See the 2 rectangular buzzers.

  Finally a picture of the nice screw down back.