I don't own one, but handled one this past fall. I was immediately caught by the different rib, and was sure it was a browning. I went over to the guy who had brought it and he let me check it out. I was hoping it was a 100, but 99 ar is what it was. It is supposedly set up the same as the 100 minus the obvious adjustable rib and non droppable trigger. I liked the gun, and would probably by one if the price was right, but would prefer a decent 100. The guy who had it was looking for a 100 when he came across this. He had to order it out of state and had it shipped. There aren't a whole lot of them from what he said and I believe he told me he payed 2100. It was definitely a nice gun if your looking for a 100 but not completely against a different gun, it sure is nice.
Yes they are a special run Browning that is being offered by a few dealers. Just think of it as a 99+ without the cheesey recoil system. The other great thing is that it is available without all of those useless holes in the barrel.
They are nice shooters and you can get POI adjustments in the 60/40 to 80/20 area. Have a reputable stock guy install a adjustable comb and you'll be in business.
BTW, they are available with either a 32" or 34" barrel.