As a newbie I just read this posting, being uk based I can perhaps clarify this model year dilemma.
When the e type was first produced the UK system for allocating the registration number plates ran from January till December and hence the cars were known by the calendar year I.e 1961'1962'1963' Model year etc however in 1967 the government tried to give our automotive industry an economic boost as cars were not selling too well. The system they came up with was to create two new registration dates that exist to this day, ie August and March. it was hoped that by having two model years, new car buyers be encouraged to change their car more frequently.
So those cars produced in March 1968 were known as 1968 Model year and those produced in August 1968 were known as 1969 model year and so it has been perpetuated ever since. The knock on effect in the uk is that cars with August registration number plates are worth more money.