Complex sentence: The identity of the sitter remains unknown and art historians have looked for clues in the pattern of three palm leaves, with a two dark feathers bound by ribbon, in her sleeve, which may represent the coat of arms of her family or her suitor's.
Split into simpler sentences: The identity of the sitter remains unknown and art historians have looked for clues in the pattern of in her sleeve. Undoubtly a heraldic design, its three palm leaves, with a two dark feathers bound by ribbon, would have represented the coat of arms of her family or her suitor's.