Hi, Simon! I found that exact drink (your version) in the book "Cocktails (Metropolitan Club Washington DC)". It was published in 1920. So it precedes "L'Art du Shaker" (1925). Here are the specs:
"10.
Three fourths Scotch Whiskey, one fourth Yellow Chartreuse, three dashes of Orange Bitters, stir well."
PS: Ok, it says 3 dashes not 2. I will try it soon!
Best Regards