Thanks all. We can do a new thread, but I've learned a lot. I thought tenderloin sandwiches are the same as the butterflied sandwich mentioned, so I see now these are two different things.
I never heard of the made-rite sandwich, I like that, want to try that too.
In Ontario we don't have many local foods or preparations but one that most people know is the peameal bacon sandwich. This is the cured but not smoked pork loin, cut in thick slices, coated (whole before the slicing) in yellow corn meal (nothing to do with peas, maybe yellow pea meal was used originally), fried, and piled on a kaiser roll. It is very good with a little mustard or ketchup and some people specify a dusting of black pepper. You can add tomato slices and lettuce. Traditionally though it is eaten plain. I've tried it on different breads but for some reason only a kaiser roll will do.
The Mennonite summer sausage sandwiches from southwestern Ontario are very good and here, I've seen (in their native area) most people eat them on plain white bread, the Wonderloaf-type. And strangely, it tastes really good that way. But the summer sausage has a lot of salt and I find it hard to take that as I get older. The peameal, being commercially cured and kept cold until sold or prepared, is not too salty at all.