They cannot be other thing...
[ Linked Image ]

Origin of the pic unknown. Seems to be late XIV early XV centuries...

That is the from "The knighting of Galahad" if I remember correctly. French manuscript from the late 14th century, I think. On the right is Sir Launcelot, the left Sir Bors de Ganis and Sir Ector de Maris, Launcelot's cousins. It is in the Bibliotheque National in Paris.

Medieval Costume, Weapons and Armour by Wagner etc. depicts several figures with circular, spaulder like shoulder protection. Including some examples with scalloped border.

Wagner depicts these as metal armour and some appear to be integral with lames like a typical spaulder.

I believe this image is showing the same.

Cheers,
Steven