This report is a companion piece to the analysis by Drs. Iván Alonso and Italo Muñoz which identified problems with the parity exchange rate used by the Peruvian government to calculate the value of the lands bonds. While the formula purports to convert the original face value of the bonds in Soles Oro to US dollars using a parity exchange rate which accrues interest and is then converted back to Nuevo Soles, it suffers from a number of mathematical flaws and inconsistencies. This report by University of Pennsylvania economics professor Dr. Alan Heston includes a calculation and recommendation for the proper parity exchange rate.