But I would say that it dates to between 1957 - 1964, as Ruby doesn't seem to crop up in the available catalogues before '57.
I think that you might be right.
I have just checked and the earlier pattern books (1938 & 1940) specifically mention "Sea Green, Flint, Gold Amber, Emerald, Sapphire", "Blue on Sea Green", as well as "Amethyst". No mention of ruby.
There is no mention of colour for 1949, but the 1957 pattern book features the initials "F. A. G. B. T. R.". I would imagine that these correspond to colours and that the "R" stands for ruby. The 1964 pattern book only mentions the colour "Ruby".