It's unusual to cite a draft of something that's already been published, which is probably why no examples can be readily found.
First, according to The Chicago Manual of Style (16th ed.), 14.218 [paywall], the method of citing a draft itself is to use the phrase working paper:
- Deborah D. Lucki and Richard W. Pollay, “Content Analyses of Advertising: A Review of the Literature” (working paper, History of Advertising Archives, Faculty of Commerce, University of British Columbia, Vancouver, 1980).
There is also a use for forthcoming, but I can't see it being used in the case where something has already actually having been published.
If you cite both the draft version and the published version, I would treat it as two different works by the same author.
From Chicago, 15.18:
For successive entries by the same author(s), translator(s), editor(s), or compiler(s), a 3-em dash replaces the name(s) after the first appearance … The entries are arranged chronologically by year of publication in ascending order, not alphabetized by title … Undated works designated n.d. or forthcoming follow all dated works …
Since the working copy in this case is identical to an already published version of the same work, even if it has no explicitly given date, I would still list it ahead of the published version.
Chicago gives an example of this:
Schuman, Howard, and Jacqueline Scott. 1987. “Problems in the Use of Survey Questions to Measure Public Opinion.” Science 236 (4804): 957–59. https://doi.org/10.1126/science.236.4804.957.
———. 1989. “Generations and Collective Memories.” American Sociological Review 54, no. 3 (June): 359–81. http://www.jstor.org/stable/2095611.
This is modified if both the working copy and the published version are dated the same year.
From Chicago, 15.20:
Two or more works by the same author in the same year must be differentiated by the addition of a, b, and so forth (regardless of whether they were authored, edited, compiled, or translated) and are listed alphabetically by title. Text citations consist of author and year plus letter.
Fogel, Robert William. 2004a. The Escape from Hunger and Premature Death, 1700–2100: Europe, America, and the Third World*. New York: Cambridge University Press.
———. 2004b. “Technophysio Evolution and the Measurement of Economic Growth.” Journal of Evolutionary Economics 14, no. 2 (June): 217–21. https://doi.org/10.1007/s00191-004-0188-x.
(Fogel 2004b, 218)
(Fogel 2004a, 45–46)
In this case, since the titles are identical, the listing order would fall back to chronological, with the draft version coming before the published version.
I suspect that if multiple published editions of the same work were cited, the same technique would be employed, and only the authors names would be replaced with a 3-em dash—with all other identical information simply being repeated.
I see no reason why this would not also apply to a draft version along with a published version.
Saying that, this is only my own interpretation of the situation.
Since there is no explicit guidance, pick something that seems reasonable and use it consistently.
