Anyway, we started out looking at people passing on the street as we walked back from a local pub whose food (unjustly, alas) had won a high reputation for good quality at low prices. "Republican!" the two of us chorused as a man passed on the other side of the street. "Fine Gael!" as a group of three went by.
We couldn't say how we knew - or, of course, if we were actually right - but as we say in Ireland, we "knew by them".
Then we started transferring it to public figures. Marlene Dietrich? Fine Gael, deffo. Doris Day? Fine Gael! Marilyn Monroe? Republican!
What about politicians? Reagan? We both hesitated, then said: "Hmm... actually... Republican!" Bush? Fine Gael, without hesitation. Back to some actors: Harrison Ford? Republican! Cllista Flockhart? Ohh, of course Fine Gael!
Martin Luther King? Republican! Nelson Mandela? Republican! Che Guevara... ummm.... ummmmmmm.... Republican? Fidel Castro? Republican! Gianni Versace? Oh, Fine Gael, no question about that.
Once you started, you can't stop. Gene Kelly? Republican! And not only that you'd know by him, there's also the story of his striding up to a blacklisted writer and seizing his hand to shake it, putting his arm around the writer and turning to grin into the cameras, defying the anti-Red forceds to do their worst.
It's nothing to do with the Fine Gael party, certainly nothing to do with the Fianna Fáil party as it has become in its latter years. It's more to do with the 'set' or the 'make of a person.
And Gregory Peck? Republican! The reaction is instant (Frank Sinatra? Fine Gael! Dean Martin? Fine Gael!)
But Gregory Peck also had family form. In the year he was born, Thomas Ashe, his great-uncle or second cousin, led one of the 1916 Rising garrisons, in Ashbourne, Co Meth, eventually reluctantly laying down their arms on the orders of PH Pearse in the general surrender.
Ashe was arrested again for making a "seditions" (probably anti-conscription) speech in Longford, and was jailed in Mountjoy Gaol.
Here, he and others went on hunger strike. The warders force-fed him, and according to my mother's account (insider knowledge, as always in Ireland, where everyone has a source), because he was so tall and strong, several prison warders would pile on top of him to try to force feed him.
Like most people at the time, she believed that the piercing of his lung with the instrument used in force feeding was deliberate. He died, a nasty death from pneumonia, a few days after his lung was pierced and filled with gruel during one of the attempts at force feeding. Over in America, Gregory Peck would have been seventeen months old at that stage.
Peck ("Republican!") was a big man too, six foot three. He grew up in California, son of parents divorced when he was six, and was brought up between his mother, his father, the maternal grandmother who is the traditional haven of lost children, and military school. He went to UCLA Berkeley as a pre-med student, but discovered acting there. He would become one of the 20th century's greatest actors.
In To Kill a Mockingbird - his greatest role - he would play a quiet hometown lawyer who takes on a case he can't refuse, and is forced to challenge the set views of his neighbours (Fine Gaelers? Republicans? A mixture!) who are locked into the apartheid of 20th-century America.
But would Gregory Peck really have been a Republican or a Fine Gaeler? Ah, definitely a Republican. You'd know by him.
Lucille Redmond's ebook, Love, gripping dark and funny stories of love and revolution, is available on Amazon and iTunes