I hadn't seen, or even heard of, a rug wool gauge until friends gave me one a couple of weeks ago, and now I've seen another - or rather a drawing of one in use. (Of course, I probably wouldn't have noticed the drawing if I didn't already have a rug wool gauge, so it's not really an amazing coincidence.)
The booklet has a section in the booklet on Rug and Mat Making, using (as it says on the gauge) Greenock Rug Wool. The company used the brand name 'Greenock' for its knitting and rug wools - the mill was at Greenock in Scotland. You could buy the wool, the gauge, a special hook, and canvas in various sizes. The canvas was not printed with a design, though, as was common later, and the booklet does not give any charts - you had to make up your own design, or (more likely) make a plain rug.
My Patons & Baldwins rug wool gauge is much later than this one, and I thought that such things were only in use from the 1930s to the 1950s, roughly, so it's interesting to see the history pushed back to the 1910s.