<p>A4 Tech double wheel mouse, model WWW-23
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The forward (first) wheel of the mouse is also a button, but the wheel button of the item on this photo acts up by sending two pulses ("clicks") instead of one.
No machine-readable author provided. <a href="//commons.wikimedia.org/wiki/User:Mardus" title="User:Mardus">Mardus</a> assumed (based on copyright claims).
CC BY-SA 3.0
No machine-readable source provided. Own work assumed (based on copyright claims).