I've tried to find photographs of both King Arthur and the queens, but to no avail. It appears these are separate sketches on the same page.
I can't seem to locate a photograph showing the whole tomb of Maximilian.
I'm thinking (pure speculation) that since the bronze of King Arthur is at the tomb of Maximilian, this might have been of an exhibition with a copy of the bronze stature present along with maybe waxed figures of the queens which Sargent saw and drew -- or maybe this is the tomb.
I have found references of a copy of this bronze in France.
Anyway, the appeal for Sargent --
a 14 year old boy -- is obvious.
Sargent, Emily, and Mrs. Francis Ormond (Owner). From their brother, the artist, at his death 1925, Gift of Mrs. Ormond to the Fogg Art Museum 1937.