King actually sold Colts that they had upgraded. So yours may not have been modified after it was purchased by its original owner. It may have been sold that way by King.
They are famous for their target revolvers, and the upgrades they had performed were often much more extensive that a simple sight rib.
Also there are a variety of King sight configurations. Does your front sight have a mirror?
They're still in business, and might be your best bet for info -
http://www.kingsgunworks.com/
Here's are two examples of King revolvers, in 38spl and 22 -
http://www.gunbroker.com/Auction/Vie...Item=128725788