The Michigan coney is set apart from other chili dogs by a sauce that is built to be dry, not soupy. The Detroit-style coney sauce is a fine, loose, beef-based topping, traditionally built around beef heart ground into the mix, seasoned and cooked down so it clings to the dog rather than pooling in the bun. It is not a chili in the bowl sense and not a wet meat sauce: it is a dry, almost granular layer that holds its place on the frankfurter. That texture is the defining decision and the thing that separates the Michigan version from the looser, wetter chili-dog builds elsewhere.
The craft is in the dog, the sauce, and the order of assembly. The frankfurter is an all-beef natural-casing dog, which matters because the casing gives a firm snap that the soft sauce and bun need as a textural anchor. It is grilled or griddled so the skin blisters and tightens. The sauce, ground fine and bound with beef heart and fat for body without liquid, is spooned along the length of the dog so it coats rather than drowns it, which is exactly why the bun stays intact through the sandwich where a wet chili would have collapsed it. Then comes the fixed sequence: a stripe of yellow mustard under or over the sauce, and a scatter of finely diced raw white onion on top. The onion is not a garnish, it is the sharp, cold, crunchy counter that cuts a rich, dry, savory meat layer. The bun is steamed soft so it compresses to the dog rather than fighting the snap of the casing. This is fast counter food, the dogs and sauce held hot and the sandwich dressed and handed over in seconds, which the dry sauce makes possible because it does not need to be managed against a soggy bun.
The variants are tightly bounded and mostly about the sauce recipe and the order of the mustard and onion, each lunch counter guarding its own. The looser, beanless original coney is the closer relative this version is most often measured against. Both belong to the broad American hot dog family, and those relatives deserve their own articles rather than being crowded in here.