Ben,
It's interesting, then, that Kirby choee to date it's first Classic units as 1969. Even though the official release wasn't until February 1970, I wonder if some were sold from August 1969 to that time albeit on a smaller level?
It does remind me, though of many cornerstones of buildings. Generally speaking, the building was not actually put to use until the following calendar year than what is on the stone due to the time it took to construct the building. While it's not apples and apples it provides some reasoning behind Kirby's decision to put "1969" on the early tags of the Classics/ICRs. In this case, one could say, then, that the Kirby Classic was designed and first manufactured in 1969 and was released for mass sales in 1970.
I wonder how many other cleaners have similar situations with initial production and release years?