This amulet resembles a heart or lungs supporting a wind-pipe with an upper crossbar. The sma hieroglyph means unification, and the amulet was believed to provide the wearer with an unified body in the Other World1. Such amulets are mainly in dark materials and from Dynasty 26 onwards1,2

Jasper?
H 1.9, W 1.0, T 0.4
Undated
© The Trustees of the
British Museum #EA54873

Black glass, flat back
H 2.0, W 1.0
Dynasty 26
© 2017 University College London
LDUCE-UC #38481

Black porphyry
flat back H 1.9, W 1.3
Dynasty 26
© 2017 University
College London
LDUCE-UC #38484

References

1Andrews C. Amulets of Ancient Egypt, 1994, p. 85 and Fig. 64b
2Petrie W M F. Amulets, 1914, pp. 11-12 and Figs. 17a-e