Here's a P1000 GEN1 (left) next to a P1000 GEN2 (right).
GEN1 pipettes:
- Don't have any marking that says "GEN."
- Are shorter.
- Have the bottom of their body shaped like a trapezoid.
GEN2 pipettes:
- Are always marked "GEN2."
- Are longer.
- Have a square bottom.