1955 210 two door post, six cylinder, three on a tree, Navajo Tan and India Ivory
The pulley is made from two stampings that are paired up and spot welded together. There is a small inner flange (less than 1/8") in each half which form sort of a hub. The center portion is obviously missing from yours as it has worn away. There are two such pulleys on the outside of your firewall. You can order both the pulleys and the bolts. I would replace both. From the amount of wear evidenced by your photo I would suspect that the cable is fatiqued and worn also. The replacement cable is also available from most classic car parts vendors.