Charles Rennie Macintosh watch

Needed a new battery and now needs cleaning.
It was difficult to get the back off because it is silver and soft.
The hallmark says that it was hallmarked in Edinburgh- the castle, the rampant lion means Scottish silver and the a means made in 1975. The HC is the makers mark. I cannot find who that is. 
The hallmark was made by a laser and not the traditional stamping method. You can see it is sort of double stamped. I don't know if this was intentional or a mistake. I suspect it was a mistake.