Regarding your presentation, I have only one caveat: the Webster in the image above is not, per se, a rebadged Challenger.
The Good Service shown appears to be a rebadged Parker Parkette Deluxe, but the Webster (assuming button filler; i have the same ad will post in larger form if have quiet minute) shows a side clip (presumably tabs, maybe a "Z") not the washer clip of the a Challenger. The top of the cap in the image above looks to be a fused black end not a threaded removable part. Basically, the cap looks to be Parkette (non Deluxe, 1935-6-ish) derived. Here is a Parker Parkette superimposed on your ad[...]
That said, some of the earlier Diamond Medal pens show clear derivation from Challenger family, albeit with some tweaks on plastic used. If this one has button filler (again, ad too small, though I have my larger copy to post later), then it is a style mix-- as the Parkette shown, though it resembles the Webster, is lever filler-- a theme that will be driven home solidly regarding your fluted pen shown earlier.
And, there are Websters derived from Challenger-like pens of course, though they perhaps can be more specifically attributed to derivation from... Parker Televisor ( a quite Challenger-like pen itself) rather than from Challenger, proper. More on that a bit later too.
regards
David
I would agree - I was using Challanger incorrectly. The Websters shown in that ad are button-fillers, so really they represent a mix of Parkette and other depression-era styles.
Your image of the DM's with top clip insertion (which to me vaguely evoked Rider, but now I'm not so sure), in Sears catalogues at least puts to rest my concern I'd seen that ad elsewhere (I suppose I still might have...).
The Diamond Medal Comrade pens, with the funky top-clip insertion, otherwise have classic features of the presumptive National/Barrett source pens - particularly the lever box. While I am not convinced that we know these were produced by National (maybe Fulz had some paper that showed it, but I have not seen it), I think they clearly were by the same manufacturer as the rest of the DM pens at the time.
Impressive, though perhaps not surprising, that Sears made catalogue variants for what they perceived to be different markets.
It may have been motivated as much by supply-chain issues and factors with stocking the different warehouses as it was by targetting regional markets. I am not sure. One of my projects for some point in the future is to dig into more of the extensive history of the Sears company and how it operated. One of the challenges for all of us in researching pen history is that pens were not produced in a vacuum (not even vac-fils). They were part of a number of trends in industrial, business, and legal development. Understanding the industrial background of the time, particularly in regards to things like transportation and distribution networks, sales and marketing strategies, and cultural trends, is crucial in putting a lot of pen developments in context (or in other words, I really need to brush up on my industrial history.)
John