It's a proprietary formula, but it could be cracked, I'm sure. My first job as an analytical chemist was reverse-engineering the surfactant and textile chemical formulations of our competitors.
It looks like it's similar to Brasso. Brasso is basically white spirits, kaolin clay, and ammonia hydroxide. The ammonia works as a strong reducer to counteract the oxidation on the brass. The kaolin clay is a very mild abrasive and the white spirits works like a wetting agent to keep everything mixed.
So, as a guess, I'd think that Nevr-Dull is similar, but they're using a higher boiling solvent. From poking around I think it's 1-heptanol. The MSDS has a boiling point of 343-degrees, and specific gravity of 0.805, and that it's soluble in water. They mixed in some mineral spirits, which will throw off the boiling point and specific gravity a bit, but 1-heptanol boils at 348-degrees and has a specific gravity of 0.818. Close, but not exactly the same. And it's not very soluble in water.
I suspect they put in a reducing agent, probably ammonium hydroxide or something similar. And use cotton wadding instead of kaolin clay for abrasiveness.
There are contract labs you could send the fluid portion to that would tell you what's in there for not a lot of money. To reverse-engineer the formula, as in how much of what ingredient, is a bit more involved and much more expensive. But for the cost of doing the analysis you could probably buy yourself a lifetime supply of Nevr-Dull.