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PANAMA - 1949-50 COLOUR TRIAL PROOFS 1949 200th Anniversary of St Xavier University set & 1950 Carlos - Malaria eradication set, in non issued colours (as SG 505/508), 'WATERLOW & SONS - SPECIMEN' overprinted and punctured with a security hole. Never hinged - without & without gum. Seldom seen or offered,  from a Waterlow limited print run.  Lovely (4 proofs)