Moses Roberts's will (General)
According to HG Nicholls' 1858 book "The Forest Of Dean", "Prosper" is mentioned as being worked from at least 1753.
http://www.forest-of-dean.net/ebooks/gutenberg/24505/24505-h.htm
And according to this recent thread from another Forum it still is !?.
http://www.welshcoalmines.co.uk/forum/read.php?4,37065,40484