Pictured above are two varieties of the 1930-31 hub cap A-1130-D.
Shown on the left is the one-piece stainless steel hub cap A-1130-D(1) used in early 1930. The -D1 cap has a first drawing date of January 10, 1930
Shown on the right is the later 1930-1931 two-piece stainless steel hub cap A-1130-D2. The -D2 cap has a first drawing date of August 11, 1930.
The pic above shows the construction of the -D suffix hub caps. In the early D1 cap, there are 20 attaching tabs which are part of the single stamping.
In the later D2 cap, there are 10 attaching tabs which are part of the cadmium plated steel inner reinforcement.
Also note in the close-up above that the Ford script is stamped through both the inner and outer metal layers after they are assembled.