On another board I was reading on this evening, someone asked this question during a discussion of making decisions by flipping a coin and received the reply, "Heads, Tails, Edges". When I read this, I vaguely recalled that meaningful messages have indeed been engraved on the edges of coins, so I ran a Google on the question and found a link to the article cited below. And I assume that if this subject interests other RR members, it will be possible to find information on numerous other examples of "messages on the third side of a coin".
Messages from money: the edges of British coins.
July 26, 2015
Here is a look at some of the message written on the outside of Britain's pound coins:
STANDING ON THE SHOULDERS OF GIANTS
This means that all human progress is by continually progressing from the works of other thinkers that have come before. The giants are those people who discovered something new, or created a new invention. This expression is most commonly associated with Isaac Newton, who said “If I have seen further, it by standing on the shoulders of giants”. Although it can be traced back to Bernard of Chartres in the 12th century
DECUS ET TUTAMEN
This literally means “an ornament and a safeguard” and is referencing the inscription itself. It was added to coins in order to prevent the shaving off of precious metal around the coin to sell for profit. The phrase itself originally comes from Virgil’s Aeneid, when it is used to describe a piece of armour.
NEMO ME IMPUNE LACESSIT
The motto for The Order of the Thistle and states “No one provokes me with impunity”. The thistle refers to ancient Scotland legend that a Norwegian Viking let out of yelp of pain when he stood on a thistle, and thus alerted the Scottish defenders to the impending attack. It is now used by a number of Scotland regiments.
PLEIDIOL WYF I’M GWLAD
From the Welsh national anthem and means “True am I to my country”.
PRO TANTO QUID RETRIBUAMUS
It translates as “what shall we give in return for so much?” or alternatively “What shall I render unto the Lord for all his benefits toward me?” and is taken from Pslam 116 Verse 12 of the Bible. It is the motto for Belfast.
DOMINE DIRIGE NOS
It is the City of London’s motto “Lord direct us”.
Y DDRAIG GOCH DDYRY CYCHWYN
“The Red Dragon shall lead” and this is the motto for Cardiff. It is also often written underneath the dragon on the Welsh flag.
NISI DOMINUS FRUSTRA
The motto for Edinburgh: “It is vain without the Lord”.
QUATUOR MARIA VINDICO
This is a reference to Britianna and say “I will calm the four waves”.
http://www.thoughtsontheabsurduniverse.com/#!Messages-from-money-the-edges-of-British-coins/cu6k/55b4f0820cf2f7a6a932e7ac