By the way, anyone who wants to see original samples of Avestan calligraphy (and a large portion if not themajority of those that are known of) should go to the site of the Avestan Digital Archive organised and hosted by the University of Salamanca:http://ada.usal.es/
It contains high quality digital images of manuscripts hosted in libraries in numerous countries in Europe and Asia. The manuscripts are written, unsurprisingly, in Avestan script, ranging from clumsy and inept near-scrawls in one or two mss to the most exquisitely executed calligraphy in others. Most also contain annotations and/or commentary in Indo-Persian script, earlier varieties of Nagari similar to Jainanagari, and Gujarati script from older varieties to modern 20th century versions, some of these also containing exquisite calligraphy.
I discovered this source as part of my searches for original data on older varieties of Gujarati and Nagari script, which I needed to flesh out my work on the early Gujarati origins of the Indonesian-Philippine post-Nagari scripts. It's well worth looking through, even if it's just to gain an appreciation of the beauty of some of the calligraphy.