Easy to open: two parts of case were not clued together, turn slightly plastic part that holds cable to help opening.
Inside: OTI6858 USB to UART converter:
- '51 MCU core
- USB 1.1 Full-Speed
- up to 3 Mbps
It has 3.3V output levels. Missing parts (L3, U3, K1) suggest some kind of optional DC-DC converter with output connected to K1.
U2 = external EEPROM for PID, VID, serial number, USB max power descriptor, LED configuration, etc.