The postbox is simply called East Markham, with ref NG22 230, although there are 5 boxes in the village, including this one http://www.geograph.org.uk/photo/4139650 less than 100 metres distant. It is a standard EIIR box on post.
Uploaded to Geograph by Alan Murray-Rust on 22 August 2014
Photo © Alan Murray-Rust, 22 August 2014. Licensed for reuse under this Creative Commons licence