@dbuckley, I too struggled to find a match among Hibernia coins. I am definitely not an expert on those things though so I assumed it was me.
Perhaps you an help us a little bit by telling us about aspects of the coin that don't come over well in your pics. Other than the letter D (and what looks like a letter G) on the front of this coin, are there any other parts of the inscription that are visible with the coin in hand? Your second pic is somewhat blurry, but looks like it is mostly worn flat. Is there anything visible to you other than the top part of a person with perhaps a flag to the left?
"If you climb a good tree, you get a push."
-----Ghanaian proverb
"The danger we all now face is distinguishing between what is authentic and what is performed."
-----King Adz