This is a 1960s hand-held, battery-powered light meter capable of metering either reflected or incidental ambient light. Made by the west-german manufacturer Mettrawatt, who much later merged with Gossen. It uses a PX13 battery which I do not have so I cannot test it.  Sold as is - nice display piece for your photographica collection. 

I am selling other photo collectables, vintage & toy cameras, reprints of historic images, many books on early photography and photographic literature in my Ebay Store - take a look by clicking on Visit Store. Follow me and check back often as I am constantly adding new items.