Having trouble identifying this. It is a 591 but has a "OB" overprint. The overprint is not listed in Scott and it looks to me like it may have been typed on the stamp. It doesn't match the font nor has the periods of others from the officials. Hard to tell from the picture but the cancellation is on top of the OB. Comments and assistance appreciated. Paul
Hi Paul - Take a look at the preface to the Scott Official Stamps section for the Philippines. It speaks to Official Handstamped Overprints and should shed light upon what you have. In essence Scott only lists press printed 'OB" overprints, not handstamped overprints.