I promised to give you the skinny. Here is a taste, snippets from a forthcoming article I have just written.
These are die proofs from the archives of the American Bank Note Company (ABNCo). Each is printed on India paper which has been mounted on a heavy Kraft paper, cardboard-like stock which was originally part of a file folder used in the archives to hold more examples of each die impression. Each folder bore a proof on the outside that illustrated the contents, and made the connection to the company inventory records. These proofs were "pulled" at the time American did the renumbering of its stock of dies sometime in the 1880s or 90s [working on pinning that down]. That was when the die numbers V36955 and V37991 were added. The relation between the numeric sequencing of the die numbers and chronology for the creation of these dies is not clear, nor is the interval between them. However, both these die numbers are lower (earlier?) than that of the die essay presently listed in Scott as 5-E1Eg.
The first of these two dies had its origin back about 1845 when it was created by Toppan, Carpenter & Co. for use on bank issued paper currency, aka "bank notes." Here is an example of the earliest dated use of this composite vignette on an unissued but signed 10 dollar remainder note of the New Orleans Canal and Banking Company, dated June 1, 1846. It bears the imprint of Toppan, Carpenter & Co., Philad(elphia) & New York. Subsequently more than half a dozen notes were designed making use of this same composite vignette.
The philatelic connection to the portrait vignettes on these notes begins nearly 5 years later than the first appearance of the composite vignette. In competition with several other bidders, Toppan, Carpenter, Casilear & Co submitted essays and a bid proposal for the 1851 contract to produce postage stamps. Their earliest design essays for the stamps (pictured here) feature portraits derived from this composite vignette die. These were placed within rococo frames.
The rejection of the rococo frame for the three cent resulted in a complete redesign of that denomination, and a complete abandonment of the Washington vignette from the composite design of 1845/6. Here are the final approved forms of the lowest denomination stamps for the issue of 1851:
You will find a lot more detail, including a color scan of the Georgetown note, here: http://goscf.com/t/34014
Some old subjects just get better and better as new data come along.