Originally issued 3 January 2013 - 20p light green Machin
definitive from counter sheets
The 20p counter sheet was reprinted on 09/02/18 by ISP Walsall, and was distributed by Royal Mail Tallents House on 23/05/18. Phosphor glows yellow under an ultra-violet lamp. By the time that was distributed, a second printing had already taken place.
The second Walsall reprint was 08/05/18: this has blue phosphor with yellow fluorescence to the transparent iridescent security ink. The examples we have appear to have a yellower shade of green.
SG U2924 as used for previous years
Cylinder blocks of 6
Date blocks of 8