The m3 is the latest addition to the stable. It uses the SC614 chip (same as the S100), but includes a built-in rechargeable lithium battery, an amplifier driving a 1W 8 ohm speaker (much louder than the S100) and an optional solar panel.
It also includes a button lock - something that was lacking on the S100. This can help prevent accidentally switching the device on when the play button is bumped unintentionally.
The top view shows a small bonus feature - an integrated torch LED - along with the micro-USB socket for charging, two status LEDs (the small holes) and an earphone socket.
The left view shows (from bottom to top) the volume buttons and the Category button (OT/Psalms/NT/Extra).
The right view shows (from bottom to top) the button lock, the reset button and the torch button.
The back view shows the optional solar panel.