The coal industry of Maverick County is located along a section of the Olmos Coal Formation immediately north of Eagle Pass. Mining operations developed by Dolch at Dolchburg and by the Olmos Coal, Coke, and Oil Company at Olmos were the largest coal producers in Texas around the turn of the 20th century.
Those photos still fade over time, plastic doesn't prevent the materials from fading or deteriorating. Pencil that's the old lead pencils, or the new graphite pencils will not fade. Graphite is the most stable form of carbon. It's color is grey rather than black, so the line will be lighter than a black color pencil, but they are not susceptible to fading, they are extremely stable.
Write or etch notes onto a wooden pencil. Wooden pencils will accept certain kinds of ink along their body, allowing you to write simple short notes, such as dates or equations. Use a pen to write these notes down and allow the ink to dry so that it is not easily smeared away by your hand. You may also use a small paper clip or other sharp item to etch notes into the wood of the pencil. This works best on pencils that are hexagonal in shape, as the flat surface makes it easier to write.