One previous owner told me there are 2-3, another that it is unique. Last sale I know of was for 13k. It looted from the Imperium Officer maturity mob, but I am told it won't loot again. From what a previous owner told me, it sounds like it was a specially designed gun, the like of which won't be made again: maybe Juan will post if he wants people to know more about it.
ps, it breaks after 15 minutes of shooting