The general lines of diachronics of Lombard and Piedmontese plural declension are drawn here:
In Lombard and Piedmontese, feminine plural is generally derived from Latin first declension accusative -as (compare Romance plurals § Origin of vocalic plurals); nouns from other classes first collapsed there; some concrete realisations are:
On the contrary, masculine plural is generally derived from Latin second declension nominative -i; this suffix eventually drops or gives rise to palatalisation or metaphonesis; some concrete realisations are: