I bought this watch over the summer primarily for the private label marking(I have several other watches marked for the same Covington, KY jeweler). Visually, it can be identified as a Bunn grade by the gold jewel settings(I need to pull the dial and check the finishing on the keyless works, which is another hallmark of Bunn and Bunn Special grade watches) and available serial number references confirm it as coming from a run of Bunn grade watches. At this time in Illinois history, 16 and 17 jewel Bunns were often intermixed in the same runs depending on when the watch was sold, and this particular one is marked as 17 jewels.
It didn't occur to me, however, when I bought the watch that it was a scarce Model 4 Bunn. All 18 size Model 4 watches are pendant set(this is their defining characteristic). From what I have been told, 18 size Illinois pendant set watches were produced for a relatively short time due to threats of lawsuits from Elgin and Waltham. Bunn grade watches in Model 4 are relatively low production. The "Blue Book"(Ehrhardt and Meggers) gives an estimate of 200 for 16j model 4 Bunns and 150 for 17j, although these numbers probably could be revised some in light of observations made in the 30 years since the Illinois book was published.
I'm quite happy to have "found" such an interesting piece already in my collection! Incidentally, I bought the watch from a friend who is also a well-known dealer and a major Illinois collector(probably one of the most knowledgeable living Illinois collectors). I'm a bit surprised that he didn't point this out to me when I bought the watch.