This pin is about the city of Kryvyi Rih located in the Ukraine. The top of the pin says:”Curved/crooked horn”. The initials FF is unknown. Could be a factory.
Kryvyi Rih is a city in the Ukraine is located near iron ore and uranium industry.
The city was founded in the 17th. century by Cossacks. The name of the city means “Curved Horn” because of the shape of a nearby lake.
In WWII the city was occupied by the Wehrmacht and was severely damaged in battle. After the war they rebuilt the city.