Most of the time, the term "barma" refers to the fancy wide collars used in formal royal costume.

However, it can also refer to the grand (and not-so-grand) necklaces worn in Kievan/Appanage period Rus. Prince Alexander and the Russian nobles (including the traitor) wear them in the classic film, Alexander Nevskiy.

From B.A. Rybakov Russian Applied Art of the 10th-13th Centuries: the 12th century "Ryazan barmy" found in a treasure hoard in Staraya Ryazan. Gold, precious stones, pearls, cloisonne enamel, filligree, granulation. State Armoury.
Rybakov12centnecklace_sm.jpg


From V.M. Vasilenko Русское прикладное искусство: Истоки и становление: 13th century oplech'e. Silver. Engraving.
Vasilenko13thcentnecklace_sm.jpg

Detail of the above, from B.A. Rybakov Russian Applied Art of the 10th-13th Centuries: described as 12-13th century. Silver. Engraving, niello, filigree, granulation.
Rabinovich12-13thcentmedallion_sm.jpg

And even cheaper knock-offs from Michael Fuller's website on Novgorod Archeology:
NovgorodMus294metalPendants_sm.jpg