Modern Vespa

While working through my spare carbs, I found that there are two different types of adjusting screws. Both have the same thread. Now which one is used on which carb?

there is actually at least another one or two long ones from the younger carbs

my bet and guess is
you cant find logic rulez for italian hardware in general
esp not in the vespa sector

try which one fits and closes the hole properly
and there you go

It looks to me like the one on top has a shorter conical taper than the other, therefore it'll open/close with fewer turns of the screw = slightly coarser adjustment.

Looks to me like the one on the bottom has stripped threads. A dellorto carb has different threads than the spaco.