Providing an original date and location for a published letter

In revising the Chicago Manual of Style CSL definitions, I’m trying to work out how to allow for both the date of an edited collection and the date of a letter. I’m thinking of using event-date if it exists in the citation (alongside event-place for the first below) – does this seem sensible? I am trying to base my implementation on APA by @bwiernik but they do not address this particular case.

Relevant CMOS examples:

  1. Adams to Charles Milnes Gaskell, Baden, September 22, 1867, in Letters of Henry Adams, 1858–1891, ed. Worthington Chauncey Ford (Houghton Mifflin, 1930), 133–34.

  2. White to Harold Ross, memorandum, May 2, 1946, in Letters of E. B. White, ed. Dorothy Lobrano Guth (Harper & Row, 1976), 273.

  3. Adams to Gaskell, London, March 30, 1868, 141.

  4. Adams to John Hay, Washington, October 26, 1884, in Adams, Letters, 361.

Jackson, Paulina. Paulina Jackson to John Pepys Junior, October 3, 1676. In The Letters of Samuel Pepys and His Family Circle, edited by Helen Truesdell Heath, no. 42. Clarendon Press, 1955.

Yes, I would use event-date here for the date of the letter, similar to how you would use it for the date a conference paper was presented if you were citing the published version in a proceedings.