Something to keep in mind if you are searching uncirculated rolls of 1973 cents. The designs used to make the 1973 cents, both obverse and reverse, were only used in 1973. So there will be small differences all over the coin compared to other years.
A good example of this is the extra large designer's initials on the reverse side, they were only like that in 1973.
Since 1973 cents have a unique design, I have been searching for a transitional error for that year, but nothing has been found. Most likely there isn't any, but I can still look!