DSV ALVIN has changed a lot since 1964, the version that this model is created from is the 1970-74 itteration, this is the version I saw and photographed during my summer working at WHOI.
In life-threatening situations, the crew compartment can be jettisoned from the main body of the craft. The Fore titanium ball along with the sail and fore ballast tanks can separate and float to the surface.
This model also reflects the EMERGENCY aspect of ALVIN.
In 1975 she dove to 12,000 feet, In 1976 she was certified for 4,000 meters or 13,124 feet.
In 2004 she comlpeted 4000 dives. And a new version is on the drawing boards.