The city of Szczecin, Poland possessed several barges for gravel transport on the Oder according to a CIA report dated 22 November 1950

An item reported that the harbour of Szczecin, Poland possessed over around 60 barges with a cargo capacity of 100-350 tons and towed by city tugs. Identified by the letters Odra-Szczecin painted in white on a red background. The barges were used for transporting gravel dredged from the bed of the Oder near Bielinek towards Szczecin where the gravel was used for the rebuilding of the town.

Source
The report was published on www.archive.org, document number CIA-RDP82-00457R006200770012-0