I grew up in Monza (Milano) during the 1970's and i had a 125 Primavera now i have (finally) a 90SS (New Zealand model). I live in Virginia U.S.A. and there are only (3) 90SS Vespa's in the entire Washington DC metropolitan
maybe the Vespa Tecnica Book can help you !
Art. Nr. 98873000
i´ve checked out for you the original code from max meyer
it is 1.268.0983
you can use this code on the ppg page ...
hope this helps you