Banja Luka Local issue. 1941, black three-line overprint ''Slobodna. Bosanska. Hrvatska'' on King Peter II 1d green and 2d lilac carmine, complete set of two, full OG, NH, VF and rare, only 1,000 sets were overprinted, several experts' signs on reverse, each stamp with RPS certificate, Mi #1-2, €2,400, Est. $700-$800 (Image)