Tetra hardware
The tetra hardware is based on the Broadcom BCM23550 (referred to as java in the device tree) chipset.
Front PCB
The front of the PCB is covered by a flexible PCB antenna used for NFC. This is connected to the PCB via a U.FL connector.
Removing the NFC antenna reveals the Broadcom SoC and on its left a shield on top of the memory.
The shield with a QR code is covering the BCM43341 Bluetooth/WiFi chip.
The unmarked chip on the top left is most likely the bcmpmu (Broadcom Power Management Unit).
Back PCB
The back of the PCB has testpoints, pogo pins and space for an unpopulated connector.
Casing
The case is closed via four screws and a silicone like glue.
The front part consists of the LCD and a transparent part for the ambient light sensor.
The back part contains a epoxied micro USB connector and a (lightly) glued in 1.59Wh battery.