First, here is the ad and auction picture of the Webley & Scott 300H&H
Now, to the 400.
Here, the general outline of the rifles is apparent.
The one major difference is the quarter rib on the auction rifle.
The Stoeger ad is for a Springfield of course, but the same stocking and features were offered for Mausers, Winchesters, Enfields etc.
Here, examples of the engraving Stoeger offered.
A comparison of the catalog style and the rifle.
Of course, there would be variations as to the subject and which engraver was actually doing the work, but one thing I noticed is the use of scrolls, as in paper scrolls, and a rope border framing the animal as well as the treatment around the floorplate release button.
Here, the buttplate style and trap are very similar. The swivels on the auction rifle are referred to as detachable "as recommended by Col. Whelen" in the catalog.
The grip cap was offered engraved with a trap if desired.