Sg 437wi 2½d Blue INVERTED WATERMARK. A superb Post Office fresh unmounted mint example. All items are described as accurate as possible. The item "Sg 437wi 2½d Blue INVERTED WATERMARK.A superb Post Office fresh unmounted mint" is in sale since Tuesday, November 6, 2018. This item is in the category "Stamps\Great Britain\George V". The seller is "avp-ltd" and is located in Tamworth. This item can be shipped worldwide.