In traditional Basque usage Guipuscoa was the provincia Check Philotea from 1821 Topatuco dute bear bada Provinciaco eusquerarequin batian Nafarroacoa Vizcayacoa ta Arabacoa They will find maybe along the Basque language of the Province i e Guipuscoa that of Navarre Biscay and Alava However as you say the Ley de Territorios Hist ricos created this new category for reasons unknown to me