There are a number of club licenses (there are 2 or 3 here in our little county) and there may still be people that hold several calls. Many years ago, the FCC issued separate calls for separate control points or station locations. A local ham had stations at his business, home and river cabin and had 3 different calls depending on where he was operating. I think the FCC stopped issuing multiple calls in the late 70's or early 80's but I don't know if the duplicate calls remained active.
Then again, the FCC accidentally changed my call to a 2x2 when I upgraded to Advanced back in the early 90's. I finally forced them to change it back but the FCC database still showed that 2x2 call as an active "alias" to my real call up until just 4 or 5 years ago. The 2x2 call no longer has a db record so still hasn't been reissued.