20l. dark grey-blue (strongly oxidized corners/pos.17), double control numbers in a distance of 2.5mm vertically (Kound. 31.3.h) tied by Syros "67" cds, P.O. not mentioned in Koundouros study. Also plate flaw white spot on the Greek border. Clear-good margins but a narrow spot at lower left. Very fine for this rare control number error. (Hellas 19dNoI).