Certainly looks like trail dies, coming off the denticles. Good eye, that should be easy to spot in mint state examples. The repunched 9 is something I had spotted before, you also see a repunched 9 in the 1929 1-cent coins (search posts in this forum, for that one)
The most spectacular trail dies in this series are on the over-polished reverse dies that were used for the 1951 specimen strikes. They basically took working dies and polished the heck out of them.