Scrolling light up sign, 1950's/60's?

This was found in my Dad's garage. He was a bit of a collector of odds and sods, and was fond of anything electrical.
It comes in a long, very heavy, metal case with a textured clear glass window at the front, and is 23 x 24 X 104 cm (approximately). Inside is the mechanism which can be used in the box or removed from it. This sign box has a perferrated tape with individual pockets (9X7cm) to place each letter (and blanks) which were then moved by the belt and rollers, between the flouresent light and the window at the front, forming a moving text for shop information. The tape concertinas in the box, so a lot of text is possible. It is in a loop so that it repeats itself. The text could be changed by moving and replacing letters. I believe it may have been used in a factory or wharehouse as part of the current sign reads "trade only supplied".
There is a large amount of text in the roll that is fitted, but comes with varying lengths of pockets for various lengths of messages I suppose.
The only label on the item is "Patent application No: 8477/55 Serial No: A523"
Thank you for any information on what this is and when it was made.