On reflection I think we can narrow the likely date the Coronation grade was introduced, theorizing that it was created sometime in 1963-1964. On the one hand we know it existed by the time the 1964-65 RTDA Almanac was issued. On the other several experts suggest that the grades above the Supreme S-100 were an artifact of the acquisition of the company by Herman Lane; this view is, if not definitive, at least completely supported by what documentation I've seen so far.
The Lane acquisition was precipitated by the death of Reuben Charatan on March 9, 1962, and took place in a series of related corporate resolutions dated November 1 and 2, 1962. When the dust settled the 2500 shares held by Esther Charatan (Reuben's widow) were reclassified as deferred (i.e. nonvoting, and not entitled to dividends), and Herman Lane held 750 ordinary (i.e. voting) shares which controlled the business. In the circumstances it seems plausible that expansions of the high end of the Charatan line would have begun to take place over the next year or two.
The Lane acquisition was precipitated by the death of Reuben Charatan on March 9, 1962, and took place in a series of related corporate resolutions dated November 1 and 2, 1962. When the dust settled the 2500 shares held by Esther Charatan (Reuben's widow) were reclassified as deferred (i.e. nonvoting, and not entitled to dividends), and Herman Lane held 750 ordinary (i.e. voting) shares which controlled the business. In the circumstances it seems plausible that expansions of the high end of the Charatan line would have begun to take place over the next year or two.