It's neutral. For example, it was used with metric system definitions: at some point the "kilogramme-étalon" was literally an object weighing 1kg (by definition

It's neutral. For example, it was used with metric system definitions: at some point the "kilogramme-étalon" was literally an object weighing 1kg (by definition, the kg was this object). You can see here a kilogramme étalon: https://upload.wikimedia.org/wikipedia/commons/0/00/Standard_kilogram%2C_2.jpg https://upload.wikimedia.org/wikipedia/commons/0/00/Standard... and a mètre étalon: https://upload.wikimedia.org/wikipedia/commons/2/22/Mètre-étalon_Paris.JPG https://upload.wikimedia.org/wikipedia/commons/2/22/Mètre-ét... Edit: for completeness sake, a litre and décalitre (10L) étalon: https://portail.polytechnique.edu/musx/sites/pf_191/files/accueil/litre_decalitre.jpg https://portail.polytechnique.edu/musx/sites/pf_191/files/ac...