I believe it's a test strike of new dies. Using soft metal like lead means less chance to damage the steel die which probably hasn't been hardened yet.

I've collected a couple of dozen of these matching different actual tokens. This one matches a fairly recent token (1995) and it's unlikely it would fool any coin rejector of that vintage so I don't think it's a slug. No particular value, but of interest to collectors who like to understand the process of making tokens.