Suggested tags

historic=archaeological_site
archaeological_site=field_system
heritage=2
heritage:operator=IE:smr
ref:IE:smr=LI040-113----
source=Esri World Imagery Wayback 2017-10-04 (DigitalGlobe WV02 2014-03-11)

Map as area. Use on the whole field(s), or rough shape, where you are able to see the (here: rectangular) cropmarks indicating the field system.