Buster, I dug one just like that and a 55 also, and posted them on this site about a month ago. It's a 1954 New Jersey year tab that covered the '52 on the full size license plate. Due to the Korean war NJ went to year tabs to renew the 1952 license plates. NJ used 53, 54, 55, 56 year tabs to renew the 1952 plates. (ALSO NJ USED A 43 YEAR TAB DURING WWII)
hope this helps. Cool find.