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 contains a wealth of information about Medieval life from the women's perspective, making it a very rare and useful document for research, as most contemporaneous documents were written by men.
Enjoy and please disseminate to other scholars who may benefit.
Dr. Gerard Cheshire.
University of Bristol.