VPI Zephyr vs Soundsmith Zephyr

  My question is whether there is a difference between these 2 cartridges. It seems the original Zephyr was designed for the VPI unipivot tonearms. Is the Soundsmith Zephyr still optimized for the VPI arms? Is the Zephyr MKIII just the latest version? That seems to make sense except my friend just bought a new VPI Classic (Dec. 2016) and paid an extra $1000 to have a Zephyr cartridge installed. The new MKIII's are $1500 so I'm sure those aren't the same. Did he get an old NOS or is there still a different cart called the VPI Zephyr?
   My interest in all this is that I have an early VPI Zephyr that I bought here used and am wondering if a re-tip is all that's needed to bring it to current spec. I use mine on an Audiomods (Rega derived) arm and don't require the special tip of the VPI Zephyr. I could ramble on about possible paths forward but getting to the bottom of my initial question will be a big help.

Thanks in advance for any info 
Have you called Soundsmith? Peter and staff are really good about detailed answers to questions, and would be able to offer more insight to your questions.