In 1954-55 the clamp was changed to stamped steel (2-pieces), it is the correct clamp. Here is one on a non-restored 54 you can see the stamped ridge. Picture 2 is the earlier version 1947-53.

http://www.flickr.com/photos/advance-design_parts_co/8130525955/in/set-72157631870734114
http://www.flickr.com/photos/advance-design_parts_co/8129347267/in/set-72157631868452754