When I was a child, my father when tossing a coin would call “heads or harps” rather than “heads or tails”. Up to 1823, Irish coins had the king’s head on the obverse and the (crowned) harp on the reverse, so “heads or harps” made perfect sense. Then British coins took over and the harp disappeared for a century. When the Irish Free State introduced its own coins in 1928, they had an (uncrowned) harp on the obverse, and various native animals on the reverse. So the call ought to have been “harps or tails”, but instead “heads or harps” made a comeback. I guess the animals all had heads, but then they all had tails as well.
The Dictionary of Newfoundland English records “heads or harps”, obviously imported from Ireland.
mollymooly 
I had forgotten about this phrase, and it’s nice to be reminded of it. I miss Ireland’s animal coins. If the salmon had been a carp, we could say harps or carps – but heads or harps has its own charm.
There were Irish pennies with harps in circulation in London until 1970 (decimalisation).
1p and 2p UK coins circulated in the republic until the euro in 2002. Higher-value coins were rare after the punt joined the ERM in 1979; beginning with the UK 20p the coins diverged in appearance as well as in value.
Characters in an O’Casey play (can’t recall which) bet on coin tosses; “Harps, a tanner!” says one, “tanner’ (I’m told) meaning a sixpence.