The PCB is using a ATMega328P (Arduino Uno type).
The Bubble display is a common cathode type, so four BC 848 transistors are the digit drivers. The segments are connected to Atmega 328 portpins. The RTC is a DS1337 conneced by I2C.
I build the PCB using my Stepcraft mill, so there is a RetroUhrCNC.plt file using HPGL code for milling.