Fairbairn's Book of Crests gives the following entries:
"Mahony, George Philip Gun. B.A., of Kilmorna. Listowel, co. Kerry, Ireland, out of the coronet of a Count of France a dexter arm in armour embowed grasping in the hand a sword, all ppr., hilt and pommel or, the blade piercing a fleur-de-lis of the last. Lasair romhuin a buadh.
Mahony, Harold Segerson, B.A., of Dromore Castle, Kenmare, co. Kerry, same crest and motto.
Mahony, John Moore, Esquire, J.P., same crest and motto."
https://archive.org/details/fairbairnsb ... ew=theater
So I'm pretty sure this is the correct identification of the crest. There are so many elements and they all match. But it's not possible to say for sure which member was the original owner but maybe you can make some additional research and find out which living years or other details would match the age of the spoon.