After much discussion with all the experts in United Nations personalized sheets, UNPI has come to the conclusion that this sheet should be listed as S18.1. We have studied the stamps on this sheet, and clearly it is the same stamp as shown on the UNPA special cancel covers (see the 7 May 2008 entry). The 90 cent international rate stamp is a much lighter blue color than the one in the S18 personalized sheet, and the the letters in "UN" are much thicker and closer together. This qualifies as a separate printing, thus the designation, S18.1.
As can be seen in this ad from the Philatelic Exporter; 25,000 sets of Pope covers were prepared for the QVC shopping channel. This equates to a least 2,500 sheets. Given that IGC also wanted Pope sheets for their covers, we estimate that about 3,500 sheets were needed. Since the Pope's U.S. visit was approximately one month from the U.S. postal rate changes, and the issuance of two new generic personalized sheets, it is likely that UNPA did not have enough sheets on hand to personalize with the Pope's picture and created a second printing of this sheet. Today, these sheets can only be bought from dealers and are not directly available from UNPA. However, the stamps are perfectly valid and can be mailed from the UN headquarters. It is also possible that some of the sheets were sold by UNPA, provided that a customer order was placed for S18 sheets between the time of the Pope's U.S. visit and before the S18 sheets went off sale. Thus, we need to acknowledge this as a separate printing and give it catalog status, unlike the Elvis sheets, which only had changes in the tabs.
Originally, we were going to number this sheet as 18a. However, several readers pointed out that S5.1 is just a change in the stamps (imperforate) and S6.1 is a variation in two stamps having the wrong denomination. Thus, to be consistent, this sheet has to be changed to S18.1. My apologies for the confusion.
I hope this brings closure to this sheet. It is time to move on to the two sheets issued on 12 May 2008.
