Does anyone know any information about this at all ? Picture added is the 1:50000 scale

Here is the cross hair if it?s exact location.

https://www.archwilio.org.uk/arch/query/page.php?watprn=CPAT18204&dbname=cpat&tbname=core&sessid=CHI1r1480cp&queryid=Q641010001563124264

Also: Foster-Smith, J.R., 1974, The Non-Ferrous Mines of Flintshire. NCMRS Occasional Publication Number 7

Foster-Smith as above:

"Tan-y-Foel
A line of old shafts on the strike of the Nant-figillt fault, (about north-west), indicates that the fault was tested for lead ore at this point. The trial was evidently not successful, though no details of the workings are known."