Michel 226y Type I PF I. – Airmail stamp, 2.50 crowns with plate error "notch in O", 1918, removed hinge

Austrian stamp 2.50 crowns from the stamp set ‘Airmail stamps for the Vienna-Krakow-Lviv-Kiev route’ with the plate error ‘notch in the O’ from 1918. Colour change of previous crown values with overprint FLUGPOST or value overprint, intaglio printing, line perforation 12½, removed hinge