This particular print is a negative image, reversed not only in tonality but from left to right as well. That is, it was produced by exposing the platinum paper in contact with an enlarged positive - the intermediary step in platinum printing before creating an enlarged negative from which to print. Edward Weston praises this manipulation, self-motivated on Modotti's part, in his Daybooks:
May 2. (1924) Tina printed her most interesting abstraction done in the tower of Tepotzotlán. She is very happy over it and well she may be. I, myself, would be pleased to have done it. She printed from the enlarged positive, so she has a negative print and shows it upside down. All of which sounds "fakey," and, in truth, may not be the best usage of photography, but it really is very genuine and one feels no striving, no sweat as in the Man Ray experiments. (Daybooks: Volume I, Mexico, p. 69)
It would be only speculation to call the print unique since one cannot be certain if the print offered here is the exact print Weston refers to. If Modotti had mounted that print upside down before showing it to Weston, one would have to assume that this print is another as it is signed and presented as photographed. However, Sarah M. Lowe, the guest curator of the upcoming retrospective on Modotti currently being organized for the Philadelphia Museum of Art for fall 1995, knows of no other example of this reversal printing.