So, you think a coat of arms is always unique? Well, you may be surprised!
Most of us have been brought up (or learned) to expect that any given coat of arms is unique and that nobody else in the world should have an identical shield. Doing so would be considered at best ignorance and at worst a form of identity theft.
However, this is not always the case.
Arms are typically unique within a given jurisdiction, such as that of the College of Arms or of the Lord Lyon, or a country or region such as any of the German states. This means that arms could very well, and have been, duplicated across jurisdictional borders. I will be using the term “jurisdiction” to refer an area where arms are covered by common rules/tradition/authority/etc.
In some cases, arms have been duplicated within the same country.
The arms above blazoned “Azure a cross Argent” are those of Greece and the French towns of Embrun, Boucq and Bousies.
Another “rule” of heraldry is that if a person bears the coat of arms of the family of “X” then that person also has the surname of “X”. This is also not an absolute rule. In countries, such as Poland, all the descendents of an armiger inherit the undifferenced arms. After a few generations, a large number of people with various surnames end up with the exact same arms just because they have a common armigerous ancestor.
The arms above are those of the ancient Polish family of Sas and also borne by the Lucki family as well as the town of Frampol.