It shall be unlawful for any person employed as an industrial police to carry any firearm or other weapon except when on duty as such industrial police. All such weapons carried while on duty shall be left at the place of employment of such industrial police.

The term “industrial police,” as used in this section, shall be construed to mean a police officer, or a person employed in any such capacity, for the protection of its property by the owner or operator of any colliery, furnace, rolling mill, water company, water supply company, water power company, electric light company, electric power company, electric transmission company, mineral, mining or quarrying company, or express company.