Hi Mike, I was very impressed when Keith K. purchased that Mullane with remains of a percussion fuze that you now own. I had an opportunity to examine both shells when they were on the market. I suspect the shorter one has a Spencer or some other cartridge lodged in the hole. I believe that it was cast from Tredegar's standard pattern. But I have never encountered a Mullane body like the one with the percussion fuze. I don't believe it is a damaged copper fuze plug, the opening looks just right for a slider. The CS Navy loved shells with percussion fuzes. So, my current theory is that it was made in 1862 for one of the CS Navy's 3 inch Rifles (just like the Army's but banded like a Parrott). During 1862, the CS Naval Ordnance Works began casting (and ordering from contractors) their own field and heavy ammo. It is a very unusual mold pattern. Congrats on adding it to your fine collection.
Below is a page I made for you Mullane. When you have time, I need 1) its body length (not including sabot). 2) Was the fuze made of white metal or brass? 3) where was it supposedly found?
Thanks, Woodenhead