Thank you all so much! I would like to say that it amazes me how much knowledge there is and how helpful people are on this forum, but it doesn't amaze me any more. I am just amazingly grateful.
And, just think, if I had asked this question two years ago, the article in Galicia Histórica would not have been available!
The window was made by Joan Espinagosa (1858-1931) "Little is known about his career, although he appears to have travelled around Europe, imported a machine from Germany in 1903 to unpolish glass and brought printed glass to Spain for the first time from Britain. He is known to have won a gold medal for a stained glass window [not the one over the Holy Door] at an Exhibition held in Santiago de Compostela." [artnouveau.eu/en/author.php?author=195] [The Exhibition was in 1909.]