David,
Heavy guns such as Parkers with #4 Frames were typically for duck and goose hunting. Many of the old duck guns just were not cared for as they should have been. This includes not cleaning the bores or over cleaning and oiling the stock! If one finds a #4 Frame gun that is shootable or at least restorable it is somewhat rare. When we factor that into a small number built (someone with TPS handy please comment as to how many) the number of surviving #4 or larger frames get pretty small.
Mark
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