16 October 2018 - 1st class deep scarlet Machin definitive M18L MCIL
The MCIL stamp was issued in a number of different booklets during 2018, all were printed on SBP2 backing paper, ie with text consisting of both upright and inverted lines.
The Harry Potter booklets are found on both SBP2 and (the remains of the) SBP1 stock, in this case inverted - the only SBP1 stamps to have inverted text.
Stamps with both backing papers are the same, the definitive stamps with blue phosphor, and with the transparent iridescent ink fluorescing yellow (see pictures)
SG number U3027. We do not expect this to have a separate catalogue listing but should be mentioned in a footnote. (See notes about U3010 etc after U3039.) On the other hand the complete booklet should have a sub-number.
(Note pictures show the SBP2, apart from the picture showing both stamps - this is for SBP1)