Sistrum with Recumbant Hathor Cow
Egypt, (664-30 BCE)
Bronze, 8 3/4 4 13/16 1/2 in. (22.23 12.22 1.27 cm)
Gift of Carl W. Thomas,
LACMA #M.80.203.135

How do we know it's not just an ordinary "recumbant cow"? It is wearing the sun-disc, Hathor's crown:

As Hathor is associated with music-making, sistra often feature her face. Boston's Museum of Fine Arts and Chicago's Oriental museum feature fine examples:

Bronze sistrum at MFA

Two sistra at OIM