Special note on PR54
Their is only one known surviving specimen from the special printing of 1875 (Scott PR54).

PSE, authenticated the stamp following a year and ten months of scrutiny that included acquiring and examining thousands of dollars worth of research materials. Records indicate that 100 of the stamps were delivered as part of the Continental Bank Note Company's special printing for the Post Office Department in 1875, but only two were sold during the nine-year period they were available for purchase; the rest were destroyed. Both of the $36 stamps were purchased by Paul Lietzow, a dealer from Berlin, Germany. He bought one in December 1879, the other in July 1880. They were not seen again publicly for more than 125 years. Until 2002, the whereabouts were not known for either of the $36 special printing newspaper stamps sold to Lietzow. The specimen authenticated by PSE was purchased several years ealier from a large newspaper stamp collection that came from Europe. The documentation includes a press copy receipt issued to Lietzow by the Third Assistant Postmaster General, A.D. Hazen, dated July 26, 1880.

In addition to the $36 stamp, the receipt indicates Lietzow also purchased that day a $48 and a $60 special printing stamp, but those have not yet been discovered. The current owner of the just-confirmed $36 stamp has not been publicly identified.