It is usual to make a ROM using a diode matrix. If the classical switching diodes are replaced by LEDs, the bits of the addressed word that have the value 1 illuminate. This allows you to view the execution of the Nand 565 program.
A new version with giant LED displays, running an intriguing algorithm :-).
Can you guess the last number before 0000 ?
Discrete finite state machine with NAND gate level logic, nice. Well done. You may be interested in the TD4 a Japanese 4 bit that is not that different to yours (https://www.youtube.com/watch?v=_Ztb2PwnVPc). The TD4 is a bit more "show" than "computational" compared to yours.