The pair of barriers, which looked like heavy concrete obstacles, seemed out of place in the 13th-floor hallway of Police Headquarters in Lower Manhattan. Spotted on Wednesday, the barriers had the aura of something official, white with blue writing in a font favored by the New York Police Department. But upon closer inspection, the messages told a different story.

“OWS,” read the big blue letters on one.

“Protecting the people from the powerful,” read the other.

The appearance of the barriers — made of plastic foam, not stone, according to one officer — roughly coincided with the first anniversary of a minutely planned police raid that cleared Occupy Wall Street protesters from their encampment in Zuccotti Park on Nov. 15, 2011.

The barriers at Police Headquarters were placed near the entrance to the office of Joseph J. Esposito, the chief of department. Chief Esposito, the department’s highest-ranking uniformed officer, was seen on video yelling orders and jabbing protesters with his baton during clashes in March.