I wonder if I would qualify? My father's mother was born in Kingstown, Dublin, now Dun Laoghaire. I've established her parents marriage in 1850, but there's no trace of her, or her sisters birth certificates. AFAIK she was born in the 1860s, she married my grandfather in Scotland, and my dad was born in 1904. An heir hunter contacted my dad in the fifties, they couldn't find my grandmothers birth details either.
During the Irish Civil War in 1922 the Public Records Office in Dublin was destroyed by explosion and fire thus destroying many records including in around half of the (Protestant) Church of Ireland records. Civil registration records did survive but registration did not take place until 1864.
If your grandmother was born before 1864 the only records would be baptismal and if the family was protestant and from Kingstown (adj to Dublin) it is most certainly that the records would be stored at the above PRO building and therefore destroyed. If the family was catholic then the records will exist, it just means trawling through parish registers.
I should add that some Church of Ireland clergymen did not send in their records, or transcribed them prior to sending them in, so it is always possible that something exists.
It should be noted that all Irish census records prior to 1901 were also destroyed.