A super GB stamp error has recently come to light. The error a 'must' for any complete GB collection shows a 'full stop' at the base of the 24p denomination. As it is a constant error only one such stamp appears in each sheet of 100 stamps. So, it is 99 times scarcer than the normal stamp (SG1629). Many serious GB stamp collectors are now realising that their collections are incomplete without this important value denomination variety. We offer the Acid Rain error stamp, together with normal stamp for comparison.