I think I accidentally had a dish of mixed grill while in Florence a few years ago. It was pretty dark outside by the time our dishes arrived, and god only knows what I was eating. It sure didn't have the mouthfeel of any meats I've ever knowingly eaten.
The typical mixed grill of Sassari. It literally means pieces, and it's made with the "poor" parts of calves (diaphragm, intestine - including cannaguru -, heart, kidney, spleen, and, most important, thyroid). It is now illegal because of the mad cow risk alert, but fiorentina (Florence's tall T-bone steak) is now legal again while zimino is not.
This does not mean that you can't find a way to buy some.