I research the Irish Family History Foundation's database. It contains 12,700,000 surviving rcds for abt 72% of Irish counties. Rcds are increasingly sparse B4 1840, rare B4 1800. Co Donegal rcds were added to this database July 7, 2009.
Note 1 - Without a KNOWN county, the chance of an ancestor's rcds NOT being in this database is AT LEAST 30%.
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 William Lynn M 1902 (exact), Portadown CI, Co. Armagh, I found 1 rcd.
For Mary Jane McKeown M ditto, I found a matching rcd. These are highly likely for your ancestors. A view of the detailed rcd SHOULD show if they married each other. If so, this validates the rcds. The view MAY also show their parents' names as well as other info. This is useful in validating the bride and groom's B rcds.
For William Lynn B 1877 +/- 4 yrs, Co. Armagh, with the father's name unknown, I found 1 rcd in 1876. The father's forename was William. If this matches the father's forename found above, it merits a detailed view.
For Mary McKeown B 1881 ditto, I found 42 rcds. Within this set, there are 3 Mary Janes: 1877 and 2-1880. Father's forenames were Hugh, William, and William. The latter 2 may be duplicates. Ditto.
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.