Re Bryn-y-Felin Copper Mine(dissused) o/s map1840 - 1918 (or whatever).
After many hours of gleaning the interwobble only only managed to find out that the Powder house/Magazine I pointed out to David was dated 1540 (Tudor ish).... There also appear to be two other disused shafts to the South, above the Bridge house on the same map, with a level twenty odd metres North of said house .
Anyway just thought I'd put in my pennyworth ramblings.
Hwl y nos
Lazy-Jason
LLan-Ystum-Dwy
::)
When the going gets tough.... Hide!!!