A female mould having a forming cavity inside which a concave object can be formed, comprises: an annular forming element extending about an axis and delimiting the forming cavity about said axis; a plate element which delimits the forming cavity transversely to said axis, the plate element having a reference surface extending transversely to said axis externally of the forming cavity; a peripheral annular component at least partially surrounding the annular forming element. The annular forming element abuts against a first portion of the reference surface of the plate element. The peripheral annular component abuts against a second portion of the reference surface of the plate element.