1867: 6 d lilac, watermark Spray, plate 6, lettered ”KI”, IMPERFORATED, large margins, centrally cancelled with «466 - LIVERPOOL 28 MY 68 (?) duplex cancellation, in fresh preservation. Karl-Albert Louis explains in his photo certificate in detail how it could occur that a stamp with a central sheet postion remains imperforated while the other stamps of the sheet got the proper perforation. Only a few copies of this great rarity are recorded so far!