CP-21-075 was the first 1956 model, shipped 8/15/55. This boat (and those numbers that followed) incorporated all of the new 1956 features - most notably the red/black upholstery, two hatch handles, etc.
A lot of people think there shipping date on the their hull card denotes the model year, but it does not. Like Al said, without seeing the entire production run (which was published a few issues ago in the Brass bell for the 21' Capri's) it is difficult to know.
1923 Hackercraft 23' Dolphin
1924 Hackercraft 33' Runabout Evangeline
1938 Gar Wood 22' Streamliner Empress
1952 Chris~Craft 19' Racing Runabout #363 Thunderstruck
Boats in the shop:
1942 Chris~Craft 17' Barrelback #71939
1957 Chris~Craft 19' Capri #499