Hi Phil. The Pan Duo use to be made alongside the Pan Familia. The Duo means a two berth and a front kitchen. Eventually the Pan Duo became a Pan Duo T in the early 90s. The T means it has a built in toilet.
The Pan Familia is a three berth, a family van with a side kitchen. Hymer eventually started calling them all Familias in the late 90s when they renamed the 3 berth the 310 (no toilet) and the 320, a two berth with a front kitchen and a built in toilet.
The overall dimensions of the Pan range, eventually the Familia range, have not changed that much until 2010 when the height of the Familia, along with the rest of the Eriba Family, grew 60 mm taller.
Randa