The pic below shows the two styles of 1930-31 closed car front belt rail finish panels. This panel is sometimes referred to as the 'dash rail'.
The upper panel pictured (in black) is the common 1930-31 belt rail panel used on all coupes, sport coupes, tudor sedans, straight windshield Fordor sedans, trucks and station wagons, as well as straight windshield cabriolets.
The lower panel pictured was used on the late 1930-31 slant windshield closed cars, including the 190A Victoria, 400A Convertible Sedan, 68C Cabriolet, and 160A, B, & C Fordor Sedans.
The basic differences are the cross-car positions of the number 2 and 4 mounting screw holes, and the fore-aft length dimension of the upper panel flange at the windshield. Note that the early panel (in black) also has more 'arch' to the lower edge, and a shorter height dimension at the center bolt location.
Shown above is a comparison of the upper flange lengths at the outboard ends of the panels.
This panel was normally finished in a mahogany wood grain on deluxe models, and in a maroon color on standard passenger models.