Well, here’s the thing. A problem with medieval European art is the issue of racial othering of subjects, by which I mean, the absence of it in many cases. There’s a lot of scholarship about symbolism and color and this and that, and there are works in which it’s clear that “sometimes people have brown skin”, other works in which Black people are colored blue or purple to denote royalty/holiness, works in which a person is obviously meant to have naturally coiled/kinky hair texture, works in which a person has dark brown skin and straight hair, et cet.
The thing is, people from the Middle East and Asia (including South and East Asia) were not considered to look especially “different” than Europeans other than in clothing style and sometimes skin color. Sometimes a specific skin color is important for symbolism in medieval European art, like many illustrations for the Song of Songs/Song of Solomon, The Queen of Sheba, various biblical figures that were considered canonically dark-skinned until late Renaissance or the Enlightenment, or the Black Madonnas as influenced by North African and Middle Eastern works attributed to Saint Luke, et cet.
So…basically what I’m trying to say is that yes, it’s entirely possible that Caspar is meant to be specifically Chinese in that miniature, considering the Magi are supposed to be from far away. Which doesn’t mean that there weren’t European people of races we would consider “Asian”, it just means they wouldn’t necessarily have been marked as “other” in ways we would recognize today.
That’s part of why so many of the medieval manuscripts I post here are “conversion” stories, baptisms, stuff like that-because it’s about making the “other” into a Christian, which from the manuscript’s perspective, is no longer “other”. Even Renaissance paintings follow this kind of convention…for an example, here’s a small piece of an upcoming post:
The guy with brown skin in the pointy hat is “Us”. The guy with the turban being pointed at by the saint in the foreground (with halo) is “Other”, probably Muslim.
For much the same reasons that Saint Maurice is depicted as specifically Black, and specifically “Us”: European armor, arms, clothing, et cet. Not only Christian, but a Saint martyred for refusing to persecute his fellow Christians.
It’s also interesting to note that in Magi paintings, sometimes the Black King is depicted as wearing “Moorish” clothing: flowing robes, a turban, other clothing or arms/armor meant to depict a new convert; other times he’s depicted in the height of European fashion, hose, hat, doublet, codpiece, et cet. It’s actually really interesting because the age of the king and his clothing often symbolize different things-an older king implies long-standing solidarity from Coptic Christians in Egypt and Ethiopia; a younger King implies new converts and/or the Crusades, stuff like that. This isn’t ironclad; just a tendency in interpretation.
For contrast/comparison, The Court of the Tartar Khan:
It can be assumed that more or less all of these people are Asian-the “Khan” in question being one of the Mongolian Khans, empire, yada yada, that whole thing. But they are marked primarily by their clothing style. And there’s the Black musician in the foreground, of course. I’m not sure if that’s meant to be a “Tartar” robe or a European style of musician’s clothing, or something else entirely. They could all be traveling independent music contractors for all we know.
So, to come full circle, the golden robe as depicted in European Medieval Art is often associated with Asia and/or Asian influence. You can read a kind of soft overview on Mongolian influence in western art here. Some of them even have definitive Asian (Mongol or Chinese) patterns on them-trade in textiles was hot business in western Europe in the Middle Ages for sure. So, I don’t really know but it sure is fun to talk about.
If anyone wants to add to this go right ahead-I’m sure there are plenty of symbols I don’t know about.