First is a Silver 356A (1956-1959). It is an 356A for the low bumper & rounded windscreen. "Pre-A"s (1948-1955) have bent windscreens. Second is a 1959-61 356B T5. The 356B was introduced with a raised bumper and lights because of changes in US regulations. In 1962 the 356B T6 was introduced with a square nose, external fuel cap, disc brakes & other updgrades. Finally the 3rd is a 356C 1964-1965 which came with largely engine power upgrades which paved the way for the 911 | Picture from Flickr Commons