You could ask — as we initially did — why only 19 cards in the set, of course one must be missing.  But not so.  This is deliberate, because the set was issued in 2017 for the XIX International Botanical Congress.  And what a set it is:  unused, postage pre-printed 4″ x 7-1/2″ cards with impressive views of modern day Shenzhen’s various attractions.  The scan for this entry 20307899A shows the sort of vinylized cover and one of the cards.  Scans B and C show other cards for different categories, including for Bao’an International Airport.  Disclosure:  we live right across the border from Shenzhen and didn’t know half of these places existed.  Two sets are available.  Grades: 1