I've found some close-up details of a 15C linen surplice (the garment Claude throws on over his nightshirt in the Porte Rouge scene). It's from Jean Fouquet's
Pietà at Nouans, worn by a canon who is probably called Jacques, as Saint James appears to be behind him as his name-saint:
Enguerrand Quarton/Charonton also shows us
a similar garment on the donor in his
Villeneuve-lès-Avignon Pietà.