VERY RARE POSTMARK ex R.M.Willcocks collection. VERY FEW KNOWN. Previously thought to be a USED ABROAD item ex STAMBOUL but now though to be a LONDON CHIEF EXAMINER/INSPECTOR mark used for "SPECIAL PURPOSES". SUPERB UPRIGHT STRIKE. Condition as seen in scans. Very Fine for an item of this type & period. Please look at all the scans to help form your own opinion.