This is a small jar of anthracite coal, stove sort, from Pennsylvania.
There is approximately 0.77 to 0.88 pound (350 to 400 grams) of coal inside the jar. There will be some slight variation from jar to jar.
Anthracite coal, or hard coal, has the highest carbon content, the greatest hardness, and the fewest impurities.
This is "stove coal". Stove is a measurement of size, not content. The standard sizing of stove coal is 1 9/16 to 2 7/16 inches (39.70 to 61.30 millimeters). Some random pieces measured 0.5 to 2.5 inches.