Specimen 1921 Tercentenary set overprinted "SPECIMEN", the ½d. with watermark inverted and reversed (rare); 2½d. unused, the others mint. S.G. 68-76, £275+

Details
Specimen 1921 Tercentenary set overprinted "SPECIMEN", the ½d. with watermark inverted and reversed (rare); 2½d. unused, the others mint. S.G. 68-76, £275+