OK, we all know now that:
1 Diatto 2 Aurea 3 Ceirano
Let's focus on #4 now...it's not a two-word name, a cyclecar/light car builder and they made more than 1 model.
To help you in the process, we can assume it's not:
Ansaldo
Aquila
Ardita
Aurea
Barison
Bianchi
Bianchi e Negro
Ceirano
Chiribiri
CIP
CMN
Colombo
Dainotti
Diatto
FAST
Fata
FIAM
Isotta Fraschini
Itala
Fiat
Lancia
Marino
Odetti
OM
Prince
SAM
SCAT
Scirea
SIAM
SPA
Stigler
Storero
Tau
Temperino
Vaghi
Zust