It is from the Gwynedd Archives Service and is in the late David Bicks "Old Copper Mines of Snowdonia" as well as being reproduced elsewhere.
In the 1980s Eldon Pothole Club did a complete exploration and I have the write up which I will pdf as soon as I have time. Unfortunately, it tells us very little as it is written in 'cavers' speak even to re-naming the actual mine as "Dragon 1" and "Dragon 2"! It is full af references to "avens" etc. At the end it casually mentions as almost as 'aside' childrens clog prints and artifacts etc that we 'real' explorers get off on.
As most will know, there are 2 lodes, north and south. The working in the picture are on the north lode and the adit is buried somewhere on the shore of Lynn Peris. It may however be possible to reach the lower workings by descent of the open workings higher up. A potentialy suicidal occupation.
The south lode workings are all explorable, although there is a very daunting pitch of over a hundred feet, and exit from the south lode adit is impossible due to a grill over the portal. The hacksaw brigade appear to have missed this one!
The last edition of "Old Copper Mines" did not sell very well, maybe as a result of picture of me appearing in it putting people off. So it may be posible to pick a copy up at a knockdown price somewhere, first port of call should be Mike Moore.
RF
My avatar is a poor likeness.