Tried this question earlier with no response. Here goes again. I have two solid rubber tires 30" x 3 1/2". Made by the same manufacturer. One tire has the four lug brackets welded to it. The other has a complete flange or ring welded to it with the four lug holes drilled in it. Anyone want to venture a guess? Possibly a set of dual rear wheels for a truck?

Not TT rears, as they were either 23in or 20 in. What you have is two different types of demontable solid tires, for demountable 30 x 3 1/2 front wheels, I've probrably got both types, comes from collecting accessories for almost 60 years