You are doing better than me Bob. I have never seen one. Just guessing it must be very early in production. I always wanted to know when they changed several things on the 3400. "Earlier" versions had a different rear handle anti-vibe bolt setup. The skinny long screw, instead of the hex connector between them.
The cases were strengthened too. More webbing added in the castings of the case and rear handles. Used a different oil cap also. I was surprised to find that the oil caps will not interchange either. The more commonly seen "thick rounded" style, the older had two thin tabs in the center of the cap, more like the 306 & 245.
Gregg,