Hello. I'm looking at a manual Bridgeport that's going to be for sale, but the seller was not the former operator of the machine. When going to remove the right angle attachment that is currently on it, found this. I'm only familiar with the common male hexagon drawbar. Does anyone recognize whats going on here? The inside bore is smooth and round. Not splined, keyed, female hex, etc - just smooth. And it's only about 3" deep with a flat bottom, it's not a through hole. I'm guessing it's related to some type of power drawbar that may have been removed? Or is there some type of cam-locking manual method I'm not familiar with? Thanks in advance for any help!