Talking with a Korean, apparently, the correct is 4 versions:
I removed the sticker of all my PG2003s, but according to the photo, I own all the models. Something I’m planning to do is weigh all the models to see the weight difference between them. I need to set aside some time to do this and catalog.
A fun fact about the second old model (without lead hardness indicator). In this model, when the lead is not in the clutch, the cap rises a little and the knock becomes harder, after the lead is in the clutch, the click becomes smooth again. I think this mechanism is similar to what we see in the Smash. In the PG2003 line, this is the only version that have it. The first version did not have it, and the later versions also do not have it.
In this link there might be more info »þÇÁ¿¬±¸¼Ò : ³×À̹ö Ä«Æä. However, I do not have an account. Can anyone with access share the content for us?