Just tidying up some blasts from the past (including some very ancient ones), largely for the benefit of anyone searching the site for information.
That’s a 1923 dog tax tag from Brabant, a province of Belgium between 1830-1995. It has the arms for the Duchy of Brabant, originally a state of the Holy Roman Empire established in 1183. Today, all of its former territories are in Belgium, except for the Dutch province of North Brabant.