A fab lucite letter rack block, circa 1960s to 1970s vintage...
It's a solid rectangular block of clear plexiglass (aka lucite, perspex) with five angled slots which have been infilled brown colour. Designed to hold a few select letters, business cards, postcards, photos etc. It's beautifully simple and undoubtedly from the late 1960s space age era. I'm unsure of its origins - no maker's marks. It's very striking with beautiful straight lines - hard to show in the photos.
It's in very good condition with minimal signs of age. Base has marks as you'd expect for perspex. No chips or cracks. 10cm long x 5cm deep x 5cm tall. Each slot would hold a few pieces of card at a set angle, see photos. 
Price includes P&P to the UK.