This conical cover is to fit over a lingam (or might have been worshipped in its own right in lieu of a lingam). It is of thickly-walled brass and is of conical form with a reinforced rim and a small, solid cast lingam-yoni motif attached to the base.
The lingam is a stylised representation of a phallus and is a tantric representation of Shiva. Usually linga are carved from stone.
Such lingam covers are used in puja or prayer rituals and are a visible form of the mantra namah Shivaya through which devotees invoke the blessings of Shiva.
The cover is decorative, has a fine patina and obvious age.
References
Aryan, S., Unknown Masterpieces of Indian Folk and Tribal Art, KC Aryan’s Home of Folk Art, 2005.
Aryan, S., B.N. Aryan & G. Rossi, Mukhalinga, Ethnoarte, 2011.
Rawson, P., Tantra, Arts Council of Great Britain, 1971.