Catherine's hairpin was a piece of jewelry that belonged to Catherine Langford.
History[]

In 1939, she wore it in her hair when Nazis led by Dr. Wilhelm Brücke arrived to Warehouse district 5 to use the Stargate. She still had it on when she went through the Stargate herself, to find her father, Paul Langford, after he was taken through it by the Nazis. She lost the jewelry during a fight with Serqet. After Catherine left the Temple of Aset, Serqet found and picked up the hairpin. (SGO: "Episode 2", "Episode 4")
When Aset asked Professor Langford what they should do with the other humans that arrived after them, she presented him his daughter's hairpin. Its presence revealed to him that his daughter was on the planet. He took it and told her that they prefer to fight their own battles. (SGO: "Episode 9")
Shortly after, Paul told Aset that Wilhelm Brücke will betray her and that he is dangerous. Brücke got physical with Langford, which caused him to drop the hairpin. Brücke recognized it as Catherine's and retrieved it. He questioned Paul where he got it and how it was there. After Aset had Serqet free Paul from his bindings, Wilhelm tossed the hairpin aside. (SGO: "Episode 9")