That is a nice-looking machine! It’s not a Necchi, but I won’t discount it may be Italian. Viscontea used that green a lot. The plain chrome faceplate and the flywheel/bobbin winder are spot on some models of their Visnova. Vigorelli is another Italian mfg that loved the vivid green machine. The Vigorelli zz has a chrome plate with two Bakelite teardrop knobs. They both have very squared models that are similar, but none of their machines I’ve seen are an exact match, though. I can’t find anything with a plate on the arm that looks like yours, either.
Is there anything on the underside of the machine? Also check the foot controller.
Sorry, don’t know why the font got so big. Tried to shrink it but it won’t.