Often times, myriad and mysterious are the ways of Dunhill - when it comes to stamps . There is an underlined 0 (meaning 1960, of course), but what does the 1 mean that is just below it? Was this released for sale in 1961? Was it repaired (unlikely, given that it is all original)or replaced in 1961? What ever the reasoning, this very generous Group 4 has at least 53 years of service behind it and is in amazingly fine condition.
--R. 'Bear' Graves