SPQR is a Roman symbol that stands for "Senatus Populus Quiritium Romanus" and it means "The Senate and People of Rome". The marking was used all the time to designate state property and could be found on the standards of the legions. If you've seen
Gladiator, Russel Crowe's character scrapes a tattoo of "SPQR" from his arm with a rock in defiance of the empire. In that spirit I though it would be appropriate for Pythium's flag to have a similar marking, but in this case it would stand for "Senatus Populus Quiritium Pythianus".
