I believe from my research that they originally did not have a bright plated finish, but rather a dull black finish. I am basing this on this unrestored, original paint '49 GMC 49 tail gate chain and the remnants of the original finish on the chains on both my '52 GMC and '50 Chevy trucks.
Here is what I did with the original chains on my GMC. 52 GMC tail gate chain I used Ospho to restore the black phosphate finish. You might be able to use Naval Jelly to accomplish the same black finish. The cover is from Jim Carter and looks just like the original complete with the ribs and drain holes. cover

Last edited by Huck; 02/05/2014 10:35 PM.