Great Britain 1961 2½d-1s6d Post Office Savings Bank Centenary imprimaturs, SG623/5A varGreat Britain 1961 2d1s6d Post Office Savings Bank Centenary, SG623 5A var Imperforate Imprimatur Set A very fine unmounted mint set of three imperforate imprimaturs, issued to mark the centenary of the Post Office Savings Bank (18611961). Each stamp bears the official "NPM IMPRIMATUR" handstamp on the reverse, indicating origin from the National Postal Museum archive. The set includes: 2d (red) featuring Queen Elizabeth II and stylised thrift plant