Working with a text that makes extensive use of a secondary source that will be given in block quotation and cited. The secondary source, however, contained many original source citations which are to be included. We'll note the secondary source and not go straight to the original source as this is a new edition of a previously published work for which the author was known to draw from that secondary source.
Effectively distinguishing for the reader between these various sources within the block quotation is the issue. In the original 1950s edition, the author and editor (at OUP) were a bit careless with their citations, and some of what the author, who was not an academic, used from the secondary source was reproduced verbatim but sometimes without quotation marks or without being set in block quotation.
This is to be corrected in the new edition where all excerpted material must be clearly presented as such. For a lengthy passage taken from a secondary source, block quotation will now be used but it is crucial to note the original source citations as well.
So the question is, how to do this exactly? Using numbered note references for a paragraph in block quotation with, for example, three internal original citations gives us the problem of the final fourth citation reference number calling out the secondary source for the whole passage, coming last and not being readily distinguishable as the secondary source encompassing all the other citations. I believe we want the reader to know this first and then having any internal original citations noted.
I've considered possible solutions such as having the end of the block quotation (a secondary source) followed by an Arabic reference number to note the secondary source, and then for all the internal original citations to use symbols as reference marks. Or, placing the final secondary source reference number in brackets. Minimalist, but it creates a distinction.
Historiography is important in this republished text but I'm unsatisfied with the way of presenting distinctions between sources (secondary and original) in Chicago style, as well as between source citations and discursive/substantive notes. All footnotes are to be given as sidenotes (margin notes) in the new edition of the work. Nothing can be rewritten.
An excerpt is below. The symbol reference marks are asterisk (*), dagger (†), and double dagger (‡). I seldom see Arabic numeral reference marks and symbols together, but it does happen, for example in Keith Houston's #Shady Characters# (2014) on p. 7, visible in "Look Inside." He used symbols for discursive footnotes and numerals for endnotes/citations. However, though this shows symbols and numeric marks together, it's not exactly my situation where a lengthy block excerpt from a secondary source contains multiple citations for the original sources.
Here's an example from the book I'm struggling with. Just for the forum, the Arabic reference numbers are in brackets. The first part here is body text:
When, in the Stone Age, metals were discovered and an attempt was made to introduce them into general use, quite an uproar must have arisen and divided people into those who accepted it, and the many who rejected it. Argument and hesitation have continued; almost up to the present day, and we can still perceive faint reverberations of this struggle. According to [And here begins the secondary source block quotation by author Stern]
the Biblical story of the building of Solomon’s temple, the sound of iron tools >was not heard,* and the Mormon temple at Salt Lake City had still to be built >without iron. No bolts of iron were permitted in the repair of the Publican Bridge across the Tiber as late as the fall of the Roman Republic.† Stone knives were used by the Jews for circumcision and by Egyptians for embalming long after they had become familiar with iron. The first successful cast-iron plow, invented in the United States in 1797, was rejected by New Jersey farmers on the theory that cast iron poisoned the lands and stimulated the growth of weeds.‡ 
The footnote (margin notes) I currently have rendered as:
. Stern, op. cit., p. 54. [Editor's note: This excerpt from the Stern report contains the following citations, the first two of which were included by Noble:
*1 Kings 6 : 7.
† Ernest W. Burgess, The Function of Socialization in Social Evolution (Chicago: University of Chicago Press, 1916), p. 16.
‡ Holland Thompson, The Age of Invention (New Haven: Yale University Press, 1921) p. 11. Citation expanded this edition.]
One issue with this approach is the Arabic reference numeral at the end of the block quotation follows the double dagger for the primary source notation. It looks taboo. To find an example of how another publisher handled a similar text in an effective and elegant manner that still largely conforms to CMOS would be invaluable at this stage.