Here’s a ghost from the past. Jamie Yakes and I published an article in the March 2016 BNR revealing the existence of a paper experiment carried out in the XB, YB and ZB blocks of the $1 Series of 1935A silver certificates: X00000001B-X00720000B—control 75 percent linen cuttings and 25 percent cotton cuttings, Y00000001B-Y00720000B—50 percent linen cuttings and 50 percent cotton cuttings, and Z00000001B-Z00576000B—50 percent linen cuttings and 50 percent raw cotton fiber. Those serial number ranges were printed early, out-of-sequence, in 1940. The remaining serials in the XB, YB and ZB blocks were printed in 1942. We mentioned that the only specimens we knew of were from the YB block from a group of low numbers that were somehow saved. A reader decided to go after the set and after scouring every resource available to him, he was able to document and acquire this lone ZB specimen from what turned out to be the elusive XB and ZB blocks. The hunt continues for one of the XBs, which were used as the control for the experiment. When it comes to rarity, you just have to appreciate whatever condition the notes arrive in.