GP battery is famous to power small devices. This is CR2016, lithium cell. Normally we called this coin cell as the size and shape is similar to a coin.
CR2016 comes with voltage of 3.0V, 90mAh of capacity, and as the code tells you, the diameter is 20mm with the height of 1.6mm.
Features
GP CR2016 cell battery
Lithium based
3.0V norminal voltage
90mAh norminal capacity
1 piece
Model: GP DL2016