This superb EXIT light originated from California. 
It is freestanding , however the front panel is spring loaded in design, for access to change the bulb, this would make it easy to drill through the back panel and wall hang it. 
A great design, all metal (except for the letters), as opposed to the British ones that are usually all Perspex or glass on the front panel. 
One of the nicest we have had. 
It has been rewired in black twisted flex with an in-line switch and PAT tested by a qualified electrician. 
Measurements: 31 x 9.5 x 20.5cm high