Actual mine name unknown.

David James in WMS47 writes:

Two water-filled shafts and several collapsed adits are present along the north-east flowing tributary of Nant-y-Crug around SN 855 831. The workings lie approximately on trend with both the Sigenlas Lode and the N-S lode at Pant Mawr (NGR SN 852 823) and could have been driven towards their intersection. There is not much spoil. The mine site lies on a gentle anticline in rather shaley rock

In WMS48, Bick writes:

With reference to Item 37, last N/L, David Bick provides the following response: ‘North of Pantmawr, otherwise Braces - David James has enquired about old workings at NGR SN 855 831. This was Nant y Gog. Far from it being unknown, you can read about it in ‘The Old Metal Mines of Mid-Wales’, Part 6, p.27. There may be more in Clwyd Record Office, where I got the details.’

Confusingly WMS N/L 55 notes:

North Nanty is almost certainly at SN 855 831. Two short reports under this name, by Capt. Edward Williams, which appeared in the MJ in 1862 and 1863 appear to refer to work in an adit, but also mention “the engine-shaft in the old mine”. David James tells me that there is little to be seen there today.