2 x 4.7″ QF Mk4 on Mk3 mountings to start with and 2 6″ BL Mk7 on P8 mountings later. The degree markings on the gun mounts do not appear to correspond with a compass in any way, the 0 on the ring in the fourth picture is pointing SSE.
Rerwick Battery is a scheduled monument. Rerwick Head, coastal battery (WW2) and camp, East Mainland, South Ronaldsay and Burray, Orkney Islands (ancientmonuments.uk)
Pictures in gallery below are from 2002 (except last one)
Pictures showing surviving studwork in BOP from 2003. The stairs in the picture have now completely rotted away. Some of the studwork is still present. (2022)
Pictures below from 2019 showing some damage to searchlight house no.2 and drainage works to the Fire Command Exchange.
