Your all half right, it is the 5.7, but not the model you think. I thought it was the IOM but it is not. The model used is the 5.7 Tactical with 8 grip points on the slide.
The IOM looks the same since it has the bubble trigger guard but has a different slide. The IOM's are difficult to get and are going for over $1,200+ I bought mine for $1,150 last May. The correct Tactical model is VERY hard to find as there are fewer than 500 in the US and will sell for $3,000 at least.
I would post pics of my 5.7 with a Matsuo launcher on it but I am on my Iphone, so a search for my posts and you'll find my show off thread with the pics of my 5.7 and CX4.