"Catherine the Great tiara." Not unless she was a very recent bride. Faux bridal crown, yours for 65 GBP. http://www.tiarasandcrowns.com/product_info.php?products_id=142&osCsid=14bd3ce5df8be626922b9d2646685561
The diamond tiara of Queen Amelie of Portugal, nee Orleans. Designed as a classic diamond pinnacle tiara, with fleur de lys spacers, due to her French heritage. She married Carlos, Prince Royal of Portugal on 22 May 1886.
Number 1 Pick. Ruby Tiara (1 of 2). If this wasn't actually pink Spinell It would be my first Ruby Tiara. The set is damned near perfect except for the pink....And since this is my dream collection, I'll just call it Red and be happy!! More info here: http://orderofsplendor.blogspot.com/2013/10/tiara-thursday-bagration-parure.html
Another picture of THE SMALL IMPERIAL CROWN OF RUSSIA - Oppositely to other Imperial regalia the Small Imperial crown belonged to the Empress that wore it. This crown was created in 1856 by Russian Court Jeweler and made from silver and diamonds to Alexander II's wife, Maria Alexandrovna who later presented it to her beloved daughter-in-law Dagmar-Minnie-Marie Feodorovna.