This is a Tiny Serial Terminal based on ATtiny85 and 256×64 OLED SH1122 display able to show 42 characters per line. David Johnson-Davies writes:
This article describes a text display based on a 256×64 OLED display that provides 8 lines of 42 characters per line. Its width makes it ideal for displaying text or program listings, unlike the more common 128×64 displays. The display is driven by a standard 9600 baud serial interface, making it ideal for debugging serial devices, or as a self-contained character display for a project. Both the display and serial input are handled by an 8-pin ATtiny85, and it’s based on my earlier project Tiny Terminal.
A Tiny Serial Terminal based on ATtiny85 – [Link]