CH 1924 50 years UPU 167AII - yellow gum - sheet - unused

CH 1924 50 years of the Universal Postal Union (UPU) - Old town hall in Bern,
20 Rp. red with yellow gum, Box teeth,
original sheet (folded) with 25 stamps - unused, most of time mint MNH, stamp lower right without gum (see pictures),
(SBK 167 AII, Michel 192Ay)