It is fascinating how much Queen Mary's Dorset Bow Brooch looks similar to the bow brooch made in 1855 for Empress Eugénie, and which was part of the French Crown Jewels' collection.
After this brooch was sold by the French republican government in 1887, the brooch was bought by Mrs William B. Astor, and it remained in the Astor family until the early 1990s. It was bought back by the Louvre Museum in 2008.
The main difference betwwen Queen Mary's Dorset Bow Brooch and Empress Eugenie's Bow Brooch is the series of diamond "pampilles" and tassels hanging from Eugenie's brooch. But the bow itself is very much similar, as shown on the picture below: