Catalog Number: CG-0005
This specimen started out showing about 40-50% of itself within the Limestone matrix is was embedded in. I spent a good deal of time with the air scribe to free it. I am confident that it is Metacoceras, but I welcome other opinions. The raised spines along the top side is my largest clue.
I do have another example of Metacoceras here.
From The Pennsylvanian Atlas of Ancient Life: https://pennsylvanianatlas.org/genera/metacoceras/