Clarification Regarding Irish Citizenship through Descent

Kicking this up even though it's been dead for a while.

Like the above posters, my father was before the 1956 Act (in 1948). His father (my grandfather) was born in Sri Lanka/Ceylon in 1905--the child of two people born in Ireland in 1858 and 1861 (yes, people in my family have children quite old). In case it's important, I was born in the US and my father was too.

So I'm wondering if my grandfather was already a citizen in a way that might entitle me to Irish citizenship, despite my father not being registered when I was born.

First time poster not really understanding how the forum works. I mean to reply to this thread:

http://www.immigrationboards.com/irelan ... 24653.html