Description: PS No. 4A with overprint of the new value 4.50 HRD in the place of 4 HRD. This overprint was thought necessary at the time when HP tried to differentiate between standardized and non-standardized letters. For standard letter the tariff was 4.00 HRD, for the non-standard letter the tariff was HRD 4.50. The new face value was printed using very small numerals leading to potential confusion in use and the decision was made not to proceed with 4,50 HRD overprint. Only a few trial sheets were overprinted. To date no integral sheet has been offered for sale and individual examples of this overprint are very rare. This error is described in Maras Catalogue under 4C P. Excellent quality, possibly unique.