With the usual apologies for any cross-posting.
The final piece of the jigsaw puzzle has been slotted into place regarding the provenance of the language and writing system for Iberian manuscript MS408. A new paper, titled 'Reintroducing a vanished Romance language' is available here: https://www.academia.edu/44261539/Reintroducing_a_vanished_Romance_language
The manuscript includes a foldout map showing a compact geography of the Tyrrhenian Sea, including the islands of Ischia, Vulcano and Lipari. It illustrates a rescue mission from Ischia following a volcanic eruption.
Enjoy and please disseminate to other scholars who may benefit.
Dr. Gerard Cheshire.
University of Bristol.