These studies are very close to figures in Lanfranco's Triumph of the Cross
in the Cappella del Santissimo Crocifisso
, St Peter's, Rome (fig. 1).1
The two head studies depicted here may represent the same figure, and even though in reverse, could be related to the small cherub figure in the upper right section of the fresco. The female figure with her arm raised, looking upwards, could be preparatory for the draped female figure seated on a cloud, directly in front of the cherub.
1. G.P. Bernini, Giovanni Lanfranco (1582-1647), Comunita di Terenzo 1982, p. 160, no. I-B