Zt 0200 question

[res1cue]

So I recently acquired a couple of 0200s, one of which is from ebay and was made in 06, the other was a recent version

I noticed there are some minor differences between the 2, mostly cosmetic, but I did notice the older 0200 had a significantly thicker tip

Anyone know when this change occurred? Would like to pick up another one of the older ones if I can, and it helps that they are stamped with dates of manufacture