Sonoff Basic in a different form factor with the same features.
It contains an ESP8285 chip on a vertical breakout board with all the needed GPIOs broken out and labeled. There are also a couple pads on the board to solder VCC and G.
Devices bought in February 2020 come with a revised PCB where the module is in a different orientation with RX and TX blocked by the capacitor.:
Quickest way to get access to RX and TX pins.