Good question I think it was 2003 but may be out by a year.
The first wave of releases were- king tiger, tigerI,Matilda, Sherman, US halftrack, amphibian, jeep, schwimmwagen, Abrams, Bradley, Patton, Humvee.
In that first wave, the US halftrack mentioned was the M16 "quad fifties". The M3A1 personnel carrier came later.
GB
I think the stug III was also one of the initial releases. At least a very early one, when all of them were "action" grade and available at KB Toys.
I picked up a load of the early releases at KB online for something like $11 each.