550f variety, CSS 799a, "Thin 16" 1943 Surcharge of 50 Cents on SYS Central Trust print 16c, East Szechwan surcharge. Basic stamp thin '16'. From the collection of Huang Ming Fang

550f variety, CSS 799a, "Thin 16" 1943 Surcharge of 50 Cents on SYS Central Trust print 16c, East Szechwan surcharge. Basic stamp thin '16'. From the collection of Huang Ming Fang