My idea on this clock is that it was the time regulatory clock at a jewelry store which sold Heuer watches. There is a long tradition of this practice of putting the name of a watch company on the dial or the glass of a regulator clock. Sometimes the watch company did this officially but more often than not the jeweler did it as advertising. A famous and ubiquitous example in the US are clocks made by E. Howard or Seth Thomas with the name of the "Ball Watch Company" on the dials or glass. These clocks were not made by Ball and your example was not made by Heuer. They all just had the name on the dial or glass.

JohnCote