Exactly, NOTHING is ever certain. While the design is indeed Italian, the designs of Italian sword hilts were extremely influential, and these styles were incorporated either almost identically or in modified forms in many places.
The thing with Germany is that they often copied blades and names and markings from highly regarded makers in other places.
When AVB Norman wrote" The Rapier and Smallsword 1460-1820" (1980), it is a reference on sword 'hilts' cataloguing types by number and from mostly art work and portraiture. He stated it was not essential to include blade forms as these were often mostly imported and hilted in accord with local or personal preferences.
With Spanish cuphilts (17th c) while these are typically of course deemed Spanish, however the hilts were often made in Italy in Spanish provincial regions. I always found this confusing.
As you say, things in antique arms are not always certain