Watching Mr. Rogers Neighborhood with my two year old, they did a segment on how a harmonica is made. They went to a small factory owned by WM Kratt and showed the process of making their Aristo-Kratt harp. The factory was in the US and the harp had a plastic comb and screwed on cover plates. Can you say "cover plates"? Anyway, I've never seen or heard one, have you?