It is indeed identical we can say... but I believe the artdeco tiara is still in Pss Sybilla's possession. At least she loaned it, on the smaller version of the tiara, to her sister-in-law Diane Countess of Nassau for the prewedding event at Guillaume and Stephanie's wedding last October.
Is this an identical tiara or is Pss Sybilla a close friend of Sylvia D'Arenberg and lent her the tiara for this event?