As we can see, this gives us two unshaven Apostles. Even then we can't be sure who is who, because again there are no identifying names. We might say that we can identify them by the symbols of cherubim faces that appear like those of a man, lion, ox, eagle in the vision of Ezekiel. So starting top left and working clockwise these figures are: St Matthew (man/angel), St John (eagle), St Luke (ox), and St Mark (lion). So this would make St Luke and St mark clean-shaven. However, this is assuming that he Carolingian artist used St Jerome's interpretation of the symbolism in scripture, which might not be the case. There are other interpretations and St Augustine is an example of one prominent figure who had a different arrangement of the symbols of the four evangelists.
If no good information is forthcoming, then this would be my approach in moving forward from here. I would go with the idea that John is clean-shaven which is the most common attribution used today. I would then assign a name to the others somewhat arbitrarily. If we can't tell who they are, then it really doesn't matter at this point. In doing so, I might follow a progression that allows people to see them in the order that they appear as authors in the New Testament - Matthew Mark, Luke, and John. If I have understood the positioning correctly then that would make Matthew left and Mark right on the south window; and Luke left and John right on the north window. Then, and this is important, I would add underneath a nicely produced plaque or additional piece of artwork, in which both the name and accepted symbols for each evangelist, so making it clear to all who enter the church who is who. Then, by the theology of Theodore the Studite, then they are worthy of veneration.
Some might argue that we name them in the order that they completed their gospels. The problem with this is that it is a moving target. For example, my understanding is that the scholarship that suggested that Mark was the earliest gospel, which came from 19th-century textual criticism, is being revised. Lawrence Feingold's excellent book on fundamental theology, Faith Comes From What is Heard explains how scholarship is now supporting the traditional view that the four gospels were written in the order that they appear in the New Testament. If you stick with the schema of tradition, I suggest, then regardless of where the scholarship moves in the future, or where it stood in 1915 when the windows were installed, you will be on firm ground in using them to support your worship.
If I was asked as an artist to paint four originals, even in a naturalistic baroque style, I wouldn’t do them like this in the first place. In fact, I would make the characteristics consistent with those of the iconographic tradition
So, who are they? Over to you!