Inside a Google Titan Bluetooth security key

Here is the key before disassembly.

The key succumbed to prying very easily.

Here's the complete circuit board, which is not held inside the shell in any way, so if it breaks open, the guts fall out completely.

The battery is stuck down onto the circuit board using a sticky pad.

Here is a close up of the chips underneath the battery.

The battery is a 35mAh 3.7W lithium polymer pack

On the top of the chip is the main tactile button and a  NXP QN9021 Bluetooth LE chip.

If you look closely you can see the track for the Bluetooth antenna between the chip and the battery.

The circuit board survived a quick dunk in water, but the long term durability with regards to water or more aggressive liquids such as sweat or seawater doesn't seem good.