a greca" was made around 1075, and was sent by Byzantine emperor Michael Dukas VII to King Géza's wife. The upper part, the "Corona latina", also dates from the 11th century, and the two parts were fitted together at an unknown date, probably around 1200. Of the other coronation items, the coronation mantle and maybe also the scepter both date from the time of Saint Stephen.
You can find more information on the Hungarian coronation regalia on my page dedicated to the Hungarian regalia.
There is an excellent and detailed photo documentation of the crown and other regalia on the website of photographer Károly Szelényi (this is the material of an online exhibition put together by Bildarchiv Foto Marburg, therefore all the commentary is in German).