The shape of the amulet box on this necklace is unusual.
Kirtimukha may hold a serpent between his hands, as above, or sprouting vegetation, as often seen on the front panel of crowns, or raining jewels.
The historical buddha is seated on a lotus, calling Earth to witness with his right hand, the other holding an alms bowl. In front of him, there are two arhats.
A torgam is a sort of cupboard used to keep offerings to wrathful deities made of butter and flour called tormas. The doors above depict Mahakala, some cups made of human skulls resting on three skulls, containing tormas and other offerings (see below).
The above skull cups both contain offerings related to the five senses (eyes, ears, heart, nose, tongue).
This is most likely a piece from a ritual bone apron used for Cham dance.