Thanks for all your comments! It's nice to know that we're in a community, doing research and craftwork together!
I really do not pretend to have the “definite” answer, but I'm inclined to think that it's embroidery rather than knitting. Chris L., thanks for pointing the Spanish pillow out to me and dropping the word “long-armed cross stitch! This reminded me of some sources that were “sleeping in my archive”. I happened to make a scan of the Spanish pillow some time ago, which clearly shows the changes in direction you refer to. The changes are not only at the edges of each square, but also occur within the heraldic motives. With my knowledge of knitting, I think it's technically not possible to change directions like this.
Schneider, J. (1975), Textilien. Katalog der Sammlung des Sweizerischen Landesmuseums Zurich: Zurich: Verlag Berichthaus
The Cloisters Museum, New York, owns a similar purse, see here: Hoving, T., Husband, T., Hayward, J. (1975), The secular spirit: life and art at the end of the Middle Ages, New York: The Metropolitan Museum of Art