I refused to guess Nazzaro, because I thought it was a mistake from my side. From what I know, Nazzaro didn't exist after 1923, while Ceirano name resurfaced as a separate name (not SCAT) around 1925, so I decided they couldn't be present at the same exhibition. Anyway, no is no
At least I was right guessing the fourth company was also from Turin
P.S. I can see now that my mistake was related to Ceirano time frames.