A knife with no tracers, bugs or electromagnetic or radiation signatures.
Twenty years old when analysed by Batman (Bruce Wayne), the blade is of extremely high quality, durable, light and perfectly weighted.
While it had seen use, it hadn't seen any in years when it was returned to Cassandra Cain on her birthday by David Cain. The knife was first given to her as a present from Cain when she was a child and later returned to her by Cain when she was Batgirl. It was pivotol in her realising that Cain was her biological father and for that reason it stood as a symbol of her connection to him and she sought to destroy it.
As such it is presumed to have been destroyed after her numerous attempts to break it.