I remember it well. Must have drunk many gallons of their products!
It is in the West High Street, No 126, on the north side, and latterly it was called Strathmore Springs. It made a whole range of different flavoured fizzy drinks, including Ferguzade, which was similar to Lucozade but not quite so sickly sweet.
When I was about 8, we had some school lessons about local industries, and we were encouraged to go and look for things 'Made in Forfar' and also to look at labels on other things and find out where they were made too. In the course of investigating this I actually visited the lemonade factory, and was shown round it.
One of the features of the product labels was to say that the lemonades etc were all made using water from an artesian well, so we learned fairly early on about groundwater and aquifers.
I think it was locally owned, certainly in the 1950s, but I don't remember the owners' name. These days it is owned by A G Barr, makers of Irn-Bru, and just produces bottled water. See
https://www.strathmore-water.co.uk/https://en.wikipedia.org/wiki/A.G._Barr
