Literature: Shatalin (2021) describes on page 40 this error without isolating a separate catalog number, Pączkowski e-catalog 293.a1 (R2)
Very interesting error in the ending of the legend on the reverse of HRTR instead of HRIR (reversed T). In Shatalin's latest catalog, the error is described as the letter I (horizontally) being mistakenly scored on the stamp and then corrected to the correct vertical alignment. In any great rarity and curiosity .
