Tiny blemish in gum, seems to be from the printing process rather than marked. Unmounted mint with normal for comparison. Scarce, only 60 values known. The item "1961 Post Office Savings.Cat £600" is in sale since Thursday, June 1, 2017. This item is in the category "Stamps\Great Britain\Elizabeth II\Pre-Decimal (1952-1971)". The seller is "wickham_stamps" and is located in Bromley. This item can be shipped worldwide.