The Museo Nacional de Antropologia in Mexico has reconstructed Structure II based on drawings by George Andrews and photographs of Teobert Maler.
Paul Gendrop, citing the Andrew's reconstructive drawing, remarks: "Above the wide upper mask the bodies of two serpents intertwine (a frequent motif on this kind of entrance). And in continuation of the façade there are the remains of a "soaring" comb, with profuse openwork, whose decoration consists of a row of large standing human figures."
Paul Gendrop, Rio Bec, Chenes, and Puuc Styles in Maya Architecture, p. 101
John Hagenbuch, a connoisseur of the Rio Bec and Chenes architectural styles, sent me this fantastic photo of the reconstruction. Thanks, John!