To reinforce perf12's statement, Michel says, "Caution! MiNr: 58 I - 62 I are easily confused with MiNr. 58 -62; Expertization is recommended
!Here are some illustrations from reliable sources. First pic is from Kohl Briefmarken Handbuch Deutsche Reich 1872-1925 page 912. These are old Michel numbers. Text blocks shows Michel #s 51-59 (3pf - 80pf). Prices are given for thick printing ("Fett") on higher value stamps. Illustration at the bottom shows thick and thin printings on the bi-color (25-80pf) issues.
Second pic shows cover of the Adolf Knop book on the Reichspost issues.
Third pic shows illustration on page 9 of the Knop book. Top lettering is from lower value stamps. Middle lettering is from the early issues (thick printing) of the higher values, and bottom lettering is from the "normal" higher values.


