Read the plaque at these coordinates. A light infantry brigade is identified. Double this number. Walk due north (magnetic) this distance (in metres). Now search for the cache.
The cache is a small (0.4-litre) snap-lock style container with a green lid, and contains the usual notebook and a few small trading items.
Note the cache area is well-tended, so please be careful with the foliage when searching for and replacing the cache. Also exercise caution, as the nearby steep drop is unfenced.