GPSS marker plate, near to Heydon, Cambridgeshire, Great Britain.
A closer view of the marker seen in &lt;a href="<a rel="nofollow" class="external free" href="https://www.geograph.org.uk/photo/833270">https://www.geograph.org.uk/photo/833270</a>"&gt;TL4241 : GPSS markers&lt;/a&gt;. S/SW indicates that this is on the Sandy-Saffron Walden link, and km 24.0 is the distance from Sandy. The up-arrow indicates that the normal flow is away from the observer looking at the notice. SGE are the operators of this section - Serco Gulf Engineering of Saffron Walden. This is probably an Official Secret.
<a rel="nofollow" class="external text" href="https://www.geograph.org.uk/profile/11413">Keith Edkins</a>
From <a rel="nofollow" class="external text" href="https://www.geograph.org.uk/photo/833285">this image</a> at <a rel="nofollow" class="external text" href="https://www.geograph.org.uk">geograph.org.uk</a>; transferred by <a href="//commons.wikimedia.org/wiki/User:Adambro" title="User:Adambro">User:Adambro</a> using <a class="external text" href="https://tools.wmflabs.org/geograph2commons/">geograph_org2commons</a>.