Specs for Murata piezo-speaker

I'm trying to create an audio line-output from a Texas instruments
"Speak & Spell compact" (educational talking toy) from the 80s which
uses a piezo-speaker.

The piezo device is no longer available, and Murata (the manufacturer)
can't supply me with the specs (which I need in order to create that
line-output, replacing the speaker).
The component name is: VSB41D25-07AR

It looks similar to this:
http://www.mcld.co.uk/oddmu/tincanbass/piezotransducer.jpg

Does anyone know the specifications (capacitance, resistance etc.) of
it?

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