When I first met my future husband in 1980, we were at the American Air Base outside of Frankfurt. Close by is Zeppelinheim, where we would go to a little food wagon that served bratwurst, currywurst, and Hawaii-Toast. I used to get it every time! Now I make something similar, called Hawaiian Quesadilla. I use swiss or emmentaler cheese, ham, and pieces of pineapple, but cooked inside a flour tortilla. Same ingredients, but cooked in a skillet instead of broiled. Your retro recipe definitely brought back memories!
I Remember Hawaii-Toast!