Thanks for that info. I had been searching for 4PNs with no luck, but already picked up two 3PNs.
In your picture I missed that you have a draw bar and what looks like a collet or Arbor. The 4PN collets have a 1 in diameter body and the 3PN has a body diameter of 0.65 in. What's the diameter of what you have there in the picture?