latent edge numbers

1. The edge numbers are small numbers running along the edge of the film, in between the perf in 16mm, and just to the far side of them in 35mm. The are photographed onto the film in its manufacture, and are there to aid the negative cutter in lining up shots in the process of conforming the negative. They are sometimes called latent edge numbers to distinguish them from inked-on code numbers.
2. Code numbers are sometimes called edge numbers

Glossary of Film Terms - http://homepage.newschool.edu/~schlemoj/film_courses/glossary_of_film_terms/
reprinted with permission