I like to think that I'm quite good at identifying Machins, but this one has me puzzled, because I can't find any decisively helpful information in Stanley Gibbons Specialised, Deegam or the online Connoisseur Catalogue.
The direction of printing is sideways (see close-up detail of bottom right corner), so it's not the De La Rue printing of sheets or vertical coils (2006). The stamp certainly comes from a prestige booklet - either Enschedé (2006) or De La Rue (2007) or Walsall (2017). But which is it?
Any help would be enormously appreciated.

