If it's not metal, chuck it in the bin and get on with yer life.
Really want to know? Chuck it in the pot and see if it melts or burns on top of the melt. Expect the smell of burnt rubber, if it's not metal. otherwise, that small an amount isn't going to change your melt much, at all, if it happens to contain any lead.
Lots of stuff out there being used for weights besides lead. Pitch it and carry on.
Cheers
Trev