Some weeks back list member Dennis Ryan asked about about this topic, with little response. I've begun making inquiries to expolre the area (The old FBI instincts at work). Below is the first reply from the list master of one of the better Irish cycling websites. While by no means dispositive, it does give a starting point.
Subj: RE: Classic Irish Cycles Date: 8/1/2001 12:28:34 PM Central Daylight Time From: RapidResults@iol.ie (RapidResults) To: MasiGC3V@aol.com
One of my bikes is a 'Rapparee'. The Reynolds 531 frame was built specially for me about 15 years ago by 'Clonard Cycles' of Clonard, Westmeath, Ireland. You could write to them as they may have some knowledge of earlier frame builders.
Most of what was raced here up to 20 years ago, would have been British. I also have a 'Harry Quinn'.
There is a collector of 'penny farthing' bikes and novelty machines called 'Pete Matthews', living in Dublin. He is not the same 'Peter Matthews' as the famous British marque.
Some of our bike shops have their own brands, but these may be imported frames.
Try asking in 'http://pub4.bravenet.com/forum/show.asp?usernum(2930258&cpv=1' it's a discussion group on Irish cycle racing. Be careful not to use your main e-mail address as the list gets trawled by spammers regularly.
I'll update as more information is uncovered.
BTW I have located one source who avers to have definitive proof that the bicycle was invented in Ireland, by a gentleman named Clancy, around the time of the First Famine in the 1840's. To avoid having the technology stolen by the great usurpers, it was taken to France where it was developed and succesfully marketed. Unfortunately, Clancy was working under a French name due to visa problems and therefore many historians have mistakenly credited the French with the invention. I am confident that my research will ultimately correct the historical record on this point.