If the image in the paper associated with the "tuning fork" statement is what the person who "picked the locks" saw (which is not at all clear from the wording of the statement), then it is a case of "someone doesn't know much about ancient Egypt and is making things up."

The description given (if accurate) is a description of the sistrum. [thegreatcat.org]

And yes, they'd come in a variety of sizes. They're a percussion instrument (a type of rattle) most commonly associated with Bast and Hathor

-- Byrd
Moderator, Hall of Ma'at