From Ian Pope's truly excellent Lightmoor FoD Coalmining site, I presume this is the same Samuel, within the detailed history of the Bailey Hill Level:

"1 August 1887 Agreement Roger Whittle, Yorkley Hill, colliery proprietor and Samuel Jenkins of Bream. Whittle agrees to let Bailey Hill Colliery, upon which he holds a lease, to Samuel Jenkins. Jenkins to have free use of machinery and plant. To pay £30 per year.

28 April 1897 Samuel Jenkins died."

See http://www.lightmoor.co.uk/forestcoal/CoalBaileyHill.html

He is also listed within the following Trade Directories:

Kelly's Directory of Bream - 1870
JENKINS Samuel, coal master. Princess Royal colliery
http://freepages.genealogy.rootsweb.ancestry.com/~cbennett/bream.htm

Morris & Co 1876 Trades Directory of West Dean, within the Bream Eaves section.
"JENKINS Samuel, coal proprietor, Knockley Tump Colliery"
http://freepages.genealogy.rootsweb.ancestry.com/~cbennett/westdean1876.htm

Kelly's Directory for Bream of 1879, fully transcribed on this site
http://www.forest-of-dean.net/?Kellys_Directory_1879
http://www.sungreen.co.uk/Bream-Forest-of-Dean/1879-Kellys-Bream.htm