Regarding the Wadsworth 28-bore, I have talked with a couple of Smith collectors who have handled that gun; and, according to their account, is not very photogenic. It is described as a plain and well-used beater with little finish remaining; and also as a gun that was intended to be a 20-bore and then got a set of 28-bore barrels, mainly as a fun/interesting/project/gift to a family member.
Regarding Smith Featherweight frames, Don is correct. The identical Featherweight frame was used to manufacture the 12,16,20, and 410 bore guns; the differences between bore sizes being primarily in the size of the breech balls and locations of firing pin holes.
I also agree that the FW frame seemed just about perfect for the 16-bore proportionally; and I also failed to note that the lightweight 16-bore FW framed Smith gun I referenced earlier was featured in the LCSCA newsletter. That was a very interesting gun in that it is unusual to find a special order Field Grade; but a 6lb. 3oz. 28" 16-bore Smith ejector gun in any grade is not a common item. Most examples seen will be near/in the 7 lb. range, and many are over 7 lbs.
We will forever miss Russ Ruppel; but Russ owned a 16-bore A2 Grade with two sets of barrels (one Whitworth, one Krupp) built on the Regular frame that weighed in a 6lbs/8oz. with either set attached.