I research the Irish Family History Foundation's database. It contains 12,000,000 surviving rcds for abt 65% of Irish counties. Rcds are increasingly sparse B4 1840, rare B4 1800.
Note 1 - Without a KNOWN county, the chance of an ancestor's rcds NOT being in this database is AT LEAST 35%.
Note 2 - Only 1/2 of Co. Cork's rcds are in this database.
Note 3 - The RC church kept control over most parish rcds from Tipperary (north). These are ONLY available thru the Tipperary Family History Research center at a substantial fee (regardless of outcome).
For Marg(aret) Tierney M 1854 +/- 1 yr somewhere in Ireland, I found 7 rcds: 1853 Offaly, 1853 Cavan, 1853 Limerick*, 1854 Tyrone, 1855 Galway and 1855 Cavan.
For James Ryan M ditto, I found 36 rcds. However, only an 1853/Limerick rcd is a POTENTIAL match.
Searching 1853/Limerick parishes, I found NO matches.
For Marg(aret) Tierney B 1824 +/- 4 yrs somewhere in Ireland with the father's forename unknown, I found 22 rcds - too many to list here.
For James Ryan B 1830 ditto, I found 167 rcds - again too many.
Google the Foundation's name to lead you to this database. Register, opt to be notified as rcds are added and browse. Pls post your search results to my genforum msg.