Looking here at a used M9A1 with this type of Compensator.
It's known as a SGS style compensator. It is not a factory part and they are fairly expensive. It is most likely not attached to a threaded barrel but by an extended guide rod. It can be removed and a standard length guide rod can be put in its place if anybody dont want to use it. It wont fit on any Beretta as they vary slightly between models but it will fit on some others. Personally id love to have it and as long as they are not raising the price to much because of it then consider such a compensator one heck of a bonus on this occasion.