A  LONDON TROLLEYBUS DESTINATION BLIND from  HANWELL (HL) DEPOT. It's a SIDE BOX blind dated 29 March 1954. 

Route numers shown: 607 655 657 667. Most of the 607 part at the top is missing. The bottom end is complete with its white footer.

Side box blinds are the most collectable because they shown the route numbers AND destinations.