I would guess Self Defense Pistol, but honestly I don't know for sure. I like how it comes with the original 85C trigger, and I've been thinking about installing one of those on my Pro-Tek just because I find them more comfortable. The slide is cut a bit differently on the Pro-Tek. Another difference would be the Pro-Tek comes dehorned/deburred, which just makes it very nice to handle. All the surfaces/controls are grippy but smooth, just making it a great feeling gun overall. Overall, I suspect the Pro-Tek is just a more polished product overall, and whether that's worth the extra $$$ is up to you.