Great Britain
1963 National Nature Week Phosphor
SG637pa Caterpillar Flaw in an umnounted mint positional corner block of 6 from Cylinder 3B Dot R3/2
Bottom right hand stamp has the error
Unmounted Mint

UK GB British Stamps
Queen Elizabeth II
Pre-Decimal Commemorative Stamp Sets
Catalogue Numbers used are taken from the Great Britain Concise Stamp Catalogue
and are used with the kind permission of Stanley Gibbons Limited